Mixed ligand metal complexes (ternary complexes) involving amino acids or peptides have been investigated by synthetic, potentiometric, spectroscopic, and crystallographic methods with emphasis on noncovalent ligand-ligand interactions, and the results are summarized in this article together with the current findings.

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At the reaction centers of photosynthetic apparatus, the primary charge separation is driven by a few particular chlorophyll (Chl) species encapsulated in protein cages via coordination bonding.

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The stabilities of ternary copper (II) complexes of O-phosphoserine(SP) with different bidentate or terdentate ligands(L) and the dephosphorylation rates of ligated SP have been measured in aqueous solutions. The dephosphorylation of chelated SP, identified as a type of β-elimination, was much faster than that of noncoordinated SP, and the promotion effect was not the same for a different L(Fig.1).

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Hydrolase model catalysts which facilitates self-formation of a micelle in water were designed and synthesized: glycopeptide type with or without a chelate-forming group, N-octadecyl-N^a-[o-[(β-_D-glucosylimino)methyl]phenylmethylene]-_L-histidinamide (chelate catalyst)and N-stearoyl-_L-histidyl-β-_D-glucosamine (comparison catalyst) respectively. These catalysts were applied to hydrolysis of N-(benzyloxycarbonyl)-_L- or _D-phenylalanine-p-nitrophenyl ester in the presence or absence of a metal ion such as Cu²⁺, Zn²⁺, or Co²⁺. The addition of a metal ion did not affect the activity, of a reference catalyst to a significant extent, while it dramatically enhanced the hydrolytic rate for chelate catalyst. It was found, however, that a metal ion lowered enantiorecognition abilities of both chelate and comparison catalysts. These phenomena are discussed on the basis of chelation of metal ions with catalysts.

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The gaseous pressures of oxygen in equilibrium with that in liquid or solid samples of biologically important compounds have been estimated from the line widths of its ESR spectra, by using a simple linear relation between the line width and the oxygen pressure. From the temperature dependence of their pressures the chemical potentials of these compounds for oxygen are evaluated (Table 1) and compared with those estimated previously. The unsaturated fatty acids, water, and catechols show large values compared with those of the other compounds investigated. The time courses of the pressure in equilibrium with fatty acids were traced for about two months, and substantial decrease of oxygen pressures was observed for unsaturated fatty acids. These findings are discussed based on the biochemical functions of these compounds.

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The Schiff bases L₁, L₂, and L₃ derived from 2, 3-butanedione 2-oxime and 2-(2-aminoethyl)pyridine, histamine and 2-(aminomethyl)pyridine were prepared. The mixed ligand dinuclear copper(II) complexes [1]-[7] bridged by a nitrogen and an oxygen atoms of oxime moiety in L₁-L₃ and an end-on type N₃^- were prepared and characterized by their magnetic susceptibilities, infrared, electronic, and ESR spectra and electric conductivities.

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The ternary copper(II) complexes containing 1-methyl derivative of PQQ (1-Me-PQQ) and 2'-bipyridine (bpy) or 2, 2': 6', 2''-terpyridine (terp) were prepared in aqueous solutions or DMSO as a model for the active site of copper-requiring amine oxidase and were characterized by electronic and ESR spectroscopy. These spectroscopic data suggested that the 1-Me-PQQ ligand in the ternary complexes is coordinated. to copper with N(6) and carboxylate( 7) in the pyridine moiety of 1-Me-PQQ. J The structures of Cu(1-Me-PQQ)(bpy) and Cu(1-Me-PQQ)(terp) are quite similar to those of Cu(PQQ)(bpy) and Cu(PQQ)(terp) rep orted already, respectively. At pH 6.5-7.0, Cu(1-Me-PQQ)(terp) promotes the oxidative deaminat i on of bpnzylamirie to benzaldehyde by a factor of 5 compared with free 1-Me-PQQ, whereas, C u (1-Me-PQQ)(bpy) has no catalytic activity. The relationships between the structures a nd catalytic activities of the ternary complexes were discussed.

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The copper-containing dissimilatory nitrite reductase [nitrogen monoxide: ferricytochrome coxidoreductase, EC 1.7.2.1] was purified from a denitrifying phototropic b acterium, Rhodopseudonzonas sphaeroides forma sp. denitrificans, and its absorption spectrum (Fig.2)showed absorption maxima at 592 and 458 nm with broad shoulders at wavelength longer than 600 nm and a shoulder at 393 nm. Its CD spectrum showed positive peaks at 830, 555, and 394 nm and strong negative peaks at 680 and 463 nm. The two CD peaks at the longest wavelength are assigned to splitted S(π)→d_x2-2 charge-transfer transitions. The ESR parameters of signals due to the type I and type II Cu(II) centers showed small pH dependency (Fig.3) which corresponds to the, pH-dependency of cytochrome c oxidase activity of this enzyme.

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The mechanism for the inhibition of enzyme activity by excess zinc ions has been studied by kinetic and equilibrium dialysis methods at pH 8.2, 1=0.5 M(1 M=1 mol· dm^-3). With carboxypeptidase A (bovine pancreas), peptide (N-(benzyloxycarbonyl)glycyl-_L-phenylalanine, N-(benzyloxycarbonyl)glycylglycyl-_L-phenylalanine and N-benzoylglycyl-_L-phenylalanine) and ester (o-(N-benzoylglycy1)-β-phenyl-_L-lactate) substrates were inhibited competitively by excess zinc ions.

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The reactions of [Cu(imidazole)₃]PF₆ [5] and [Cu(imidazole)₃(CO)]PF₆ [6] with dioxygen have been examined by ¹H-NMR spectra. [5] readily reacted with O₂ at a broad range of temperature to give copper (II) complexes. Bubbling O₂ through a solution of [5] at lower than -50°C resulted in the formation of an intermediate species, which gave broad NMR signals between 7 and 15 ppm, indicative of the antiferromagnetic system. [6] did not readily react with O₂ at low temperatures By standing a solution of [6] under an O₂ atmosphere at -50°C, reddish violet precipitates appeared which hardly dissolved in usual solvents.

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In order to clarify crucial roles of an intramolecular axial base in alkylation and dealkylation reactions of vitamin B₁₂, hydrophobic vitamin B₁₂ derivatives bearing a proximal base capable of coordinating to the nuclear cobalt at the α- and β-sites, [Cob(II)(α-Im)6 C₁ester]ClO₄ and [Cob(II)(β-Im)6 C₂ester]ClO₄, respectively, and a hydrophobic vitamin B₁₂ capped with a fragment involving the imidazolyl moiety, [Cob(II)(Im: cap)5 C₁ester]ClO₄, were prepared. Their ESR spectra indicated that the three different imidazolyl moieties were completely coordinated to the nuclear cobalt, and such intramolecular coordination acted to shift the Co(II)/Co(I) redox potential to a cathodic side. The extent of potential shift was com parable to that observed upon addition of N-methylimidazole to a hydrophobic vitamin B₁₂without an axial base at a 50: 1 molar ratio. The axial base did not significantly show a kinetic effect on the alkylation of hydrophobic vitamin B₁₂'s, since the univalent cobalt has no detectable tendency to interact with an axial ligand. The imidazolyl segment introduced into the β-site inhibited alkylation reactions due to steric reasons. All the intramolecular axial bases treated in this study enhanced cleavage of the cobalt-carbon bond under aerobic irradiation conditions as originated from their steric and electronic effects.

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Lanthanoid ions give important and useful informations to characterize the two metalbinding sites (N and C) of transferrin(Tf) which plays an important role in iron metabolism of animals. Chicken ovoTf and human seroTf bound rapidly trivalent lanthanoid ions, Ln (III), forming colorless complexes, except La(III) and Ce(III). With respect to cerium, an yellow product (λ_Max≈420 nm), which was assumed to be Ce(IV)-Tf complex, appeared only on a prolonged incubation of the mixture of apoTf and Ce(III) at pH 8. La(III) ion did not bind to both Tfs. The Ln(III) complexes at the two sites, N and C, differed markedly in the metal release rate from these sites in the presence of EDTA.

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Reactions of some copper(II) complexes with hydrogen peroxide (H₂O₂) to give OH radical have been studied by use of thiobarbituric acid (TBA).
[Cu(en)₂]²⁺ has, among the copper(II) comp lexes examined, the 'highest activity toward H₂O₂. CoPper(II) complexes with polyamine-N-polycarboxylate such as... EDTA, DTPA, EDDP and EDDA do not react with H₂O₂. But they yield OH radicals by the reaction with H₂O₂ in the presence of a reducing agent such as NADH. These results indicate that these copper(II) complexes can oxidize H₂O₂ because the redox potentials of copper(II) have cha nged by ligation with polyamine-N-polycarboxylate.
Copper(II)-peptide or -nucleotide complexes can yield OH radical by the reaction with H₂O₂, but the yield of OH radical is less than that obtained from the reaction of [Cu(en)₂]²⁺ with H₂O₂. This result suggests that the OH radical generated by the reaction of copper(II)complexes with H₂O₂ can competitively react with both deoxyribose and peptides or nucleotides. Further, in Cu(II)-nucleotide complexes, the order of the activity toward H₂O₂ is that of the stability of Cu(II)-nucleotide; Cu-ATP>Cu-ADP>Cu-AMP.

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The design of the reducing systems consisting of carbon acids, bases, and (n-Bu₄N)₂[Fe₄S₄(SPh)₄] [1] was examined in relation to a biological reducing system which incorporates ferredoxin and active aldehyde. The cluster [1] was not reduced by carbon aci ds, such as benzoin, deoxybenzoin., and indene, in the presence of triethylamine or 1, 5-diazabicyclo[5.4.0]unlec-5-ene(DBU) in degassed acetonitrile, although the ligand substitution of [1] occurred in the (1)-benzoin or deoxybenzoin-DBU system.

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Artificial hemoglobin molecules are reviewed with emphasis on the contruction of allosteric systems. Metal complexes (Fe^II, Co^II and Zn) of dimeric porphyrin, which covalently linked with a metasubstituted benzene ring, have been prepared in order to mimic allosteric mechanism in hemoglobin system. These metalloporphyrins, named gable porphyrin metal complexes, bind small ligands such as O₂, CO and imidazole cooperatively in the presence of excess bridging ligands, Two subunits in gable M₂ are interacted together through the bridging ligand to form low affinity comolex (T-state). Adsorption of one oxygen on the first site causes cleavage of the intramolecular bridge. The second site binds to a bridging ligand to form the high affinity complex (R-state). The second guest binding is stronger by a factor of 31-16than the first guest binding, thus showing characteristic sigmoid adsorption. Moreover, we have constructed an artificial allosteric system, gable Fe^II₂ 2, 2'-bipyrazine complex, induced by an effector, Zn²⁺ ion.

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The authers studied the epoxidation reactions catalyzed by the synthetic metalloporphyrins for the development of both efficient catalysts and a new model system for the shunt mechanism of cytochrome P 450 (Fig.1). The maximum yields and the reaction rates of epoxidation of styrenes and cycloalkenes with hypochlorite catalyzed by Fe and Mn complexes of the fluorinated porphyrins were determined (Tables 2-5).
The Mn complex of 5, 10, 15, 20-tetrakis(2, 6-diflu orophenyl)porphyrin TF₂P (Fig.2) exhibited a high catalytic activity with the yield of 200000 turnover numbers in α-methylstyrene epoxidation in the presence of a nitrogen base, and it was found to be hopeful as a practical oxidation catalyst at least in the laboratory scale (Table 3).
In the systems of hypochlorite as an oxygen source, a sufficient stability of Fe porphyrin complexes against the oxidative decomposition is generally required for the use of the complex as a catalyst. This stability was achieved by the protection of the meso positions of the porphine core with the fluorine atoms at the ortho positions of the phenyl rings (Table 2).
The Fe complex of TF₂P was found to be suitable for cycloalkene epoxidations, exhibiting the maximum yield and the reaction rates superior to those of the Mn complex (Tables 3 and 5). The Fe complexes simplified the reaction system without the involvement of nitrogen base and, in the case of styrene epoxidation, suppressed the formation of by-products (Table 7).
It was found that, at a low level of Fe complexes as the catalyst, the initial rates of the epoxidation exhibited the substrate saturation kinetics similar to the enzymatic processes (Fig.5). Thus, the iron porphyrin-hypochlorite system could be a good model for the oxidation by cytochrome P 450.

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Cobalt Schiff base complexes are found to promote the oxygenation of nitroalkanes to give corresponding carbonyl products and (ONO)Co^III(L) (L=Schiff base ligand). The hig hest selective formation of the carbonyl product with a high conversion is achieved by em ploying a coordinatively saturated hydroxocobalt(M) complex. The oxygenation of 1-pheny l-1-nitroethane with (HO)Co^III(salen), a coordinatively unsaturated complex, in a lcohols gave the corresponding substituted benzoic acid esters together with acetophenone. The reaction d oes not proceed catalytically, because the nitritocobalt(II) complex formed is inactive. Kin etic studies of the oxygenation of 1-phenyl-1-nitroethane show that the first step may be an acid base equilibrium reaction between the substrate and the hydroxo complex giving a subst rate anion cobalt(III)c omplex intermediate. Dioxygen is incorporated into the substra te anion species to give a (1-nitro-1-phenylethylperoxo)cobalt(III) complex, which may decompose to (ONO)Co^III(L) and dioxirane, Ph(Me)CO₂, and this dioxirane further oxidizes the substra te or the substrate anion species selectively, when the peroxocobalt(E) complex is coo rdinately saturated. Otherwise, the peroxo complex in alcohols decomposes to (ONO)Co^III(L) and Ph(Me) (RO)COOH, which undergoes the Baeyer-Villiger decompositiont o the benzoica cid esters (PhCOOR). A good evidence is available from the oxygenation of 1-(4-nitrophen y1)1-nitroethane with (HO)Co (salen) in metanol, where 1-(4-nitrophenyl)-1-methoxyethyl hydroperoxide is isolated together with 4'-nitroacetophenon e and methyl 4-nitrobenzoate.

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Cobalt Schiff base complexes, which can function as models for dioxygenases as well as monooxygenases depending on the reaction medium, are now found to catalyze the dehydrogenation of p-substituted benzyl alcohols to give the corresponding benzaldehydes when t-butyl hydroperoxide is used as an oxidant. Catalytically active species is (t-Bu00)Co^III(L) (L=Schiff base ligand). The reactivity of the peroxo complex depends on the coordination number: a five coordinate peroxo cobalt(III) complex (coordinately unsaturated) shows high reactivity but self-decomposition competes with the dehydrogenation of the substrate, whereas the reactivity of coordinately saturated peroxo complexes is low but the selectivity of the dehydrogenation is high. Since no dehydrogenation of dibenzyl ether takes place with the present peroxo complex, the interaction between the hydroxyl group in the alcohol substrate and the peroxo complex may be important for the present dehydrogenation reactions.

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Mansidy showed that (dihalocarbene) (teiraphenylporphyrinato)iron(II) are obtained by the reaction of [Fe^II(tpp)] with carbon tetrahalides in the presence of a reducing agent².⁶. In this work, the reaction behavior of Fe (II) and Mn (II) octaethylporphyrin toward CCl₄ an d CBr₄ were investigated under similar reaction conditions to those used by Mansuy. The reaction of [ Fe^II(oep)] and CCl₄ in the presence of iron powder or NaBH₄ afforded(dichlorocarbene)(octaethylporphyrinato)iron(II)(3) or μ-carbido-bis[octaethylporphyrinatoiron (II)], (2), respectively. The reaction of [Fe^II(oep)] and CBr₄, even in the presence of iron powder afforded (2). (see Table 1 and Fig.1). The are attributed to a stronger reducing power of [Fe^II(oep)] than that of [Fe^II(tpp)].

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The functions of 6- and 7-propionic acid groups of prosthetic heme in hemoproteins have been investigated. Six types of heme derivatives (2-1'-2-6') were prepared by stepwise syntheses in which 6- and/or 7-propionic acid groups were replaced by methyl or acetic acid groups. These hemins were incorporated into sperm whale apomyoglobin. Comparison of ¹H-NMR spectra of the reconstituted myoglobins suggested that the 7-propionic acid grou p should or would play more dominant role for the orientation of heme in the heme pocket than the 6-propionic acid. The absence of the 6-propionic acid enhanced the rate of autoxidation of oxymyoglobin to metmyoglobin, probably due to lack of hydrogen bond network around 6-propionic acid. In addition, importance of arrangement of four hydrophobic substituents at l-4-position has been noted in heme orientation in the reconstituted myoglobins.

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A tetraheme protein, cytochrome c₃ (cyt. c₃) from Desulfovibrio vulgaris Miyazaki (Dυ. M)was investigated by ¹H-NMR. Five sets of spectra appeared and disappeared in a consecutive way in the process of reduction. This observation shows that although there are four hemes per molecule, the intermolecular electron transfer of cyt. c₃ is dominated by one-electron fourstep process in equilibrium. Thus, there are five different redox states and four macroscopic formal potentials in the whole redox reaction. It is not easy to determine the four macroscopic formal potentials because the redox potentials of four active centers are close to one another.

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Iron(II) protoporphyrin IX (heme) was coupled with a-cyclodextrin (CD) by two covalent bonds to form two types of CD-heme derivatives (Scheme 1, 2). These compounds were isolated by gel permeation chromatography (GPC) on Biobeads. In aqueous solution the CDbonded heme binds imidazole with a smaller equilibrium constant than that of the corresponding heme-imidazole complex. Probably due to the steric hindrance and the hydrophobic environment of the CD cap, these CD-bonded heme complexes formed relatively long-lived oxygen adducts in aqueous N, N-dimethylformamide at -30°C in the presence of a bulky axial ligand, such as a polymeric 2-methylimidazole. The LD₅₀ for intravenously administered CD-bonded hemin in rats was > 450 mg/kg, which was lower in toxicity than that of hemin (LD₅₀=-90 mg/kg).

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Hyperfine (hf) splittings due to the ⁵⁷Fe nucleus (I=1/2) have been observe dfor the first time from frozen-solution ESR measurements on low-spin Fe(111) heme complexes, [Fe(TPP)(OMe)₂]^- [1] and [Fe(TPP)(SEt) (MeOH)] [2], where TPP is tetraphenylporp hine dianion. Remarkable differences in the hf splitting (A₍₁₎ values of the g₁ absorption peaks (i=X, Y, Z) are found between the two low-spin speci)es: For [1], A_(x) =6.1, A_(y) = 15.6, and A_(z) = 8.6 G, while for [2], A_(x) = 18.1, A_(y) = 3.6, and A_(z) = 3.4 G. These results are analyzed within the framework of a low-symmetry crystal field model (Figs.1 and 2).

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Ethanol was oxidized to acetaldehyde with N, N'-(2-hydroxy-1, 3-propanediy1)bis[salicylylideneaminato]copper(II), [1], in the presence of base such as KOH at 40-45°C. The time course of the reaction showed the autocatalytic feature. During the reaction, the reduction of [1] was observed, and hydrogen peroxide was found to be responsible for the reduction, to give the reduced form of [1] which is catalytically more active than [1] itself.

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An attempt was made to prepare two types of metal complexes with modified cyclodextrins, by which, these complexes were expected to exhibit an enzymatically catalytic effect. One was the binuclear Cu(II) complex with α-cyclodextrin, wherein two primary hydroxyl groups standing opposite to each other were replaced by N-salicylideneethylenediamine groups. The other was the Fe(III) complex with duplicate β-cyclodextrins with a porphyrin ring interposed between them. During the courses of preparation of those complexes, the crude products had to be purified by chromatography, because several by-products were formed.

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Electronic absorption spectra for nitrosyl(protoporphyrin IX dimethyl esterato)iron(J1) (Fe(ppixdme) (NO)) complexes with stericaly hindered nitrogenous bases (2-methylimidazole and 2, 4, 6-trimethylpyridine) have been measured both at room temperature and at liquid nitrogen temperature and compared with those for Fe(ppixdme) (NO) complexes with unhindered nitrogenous bases (imidazole and pyridine). The system containing Fe(ppixdme)(NO)and hindered nitrogenous base in acetone exhibited the electronic spectra identical with those of fivecoordinate Fe(ppixdme)(NO) complex at room temperature and with those of six-coordinate Fe(ppixdme)(NO) complex with an unhindered nitrogenous base at liquid nitrogen temperature. This indicates that the hindered nitrogenous bases can coordinate to the axial vacant position of Fe(ppixdme)(NO) not at room temperature but at liquid nitrogen temperature.

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A polymerized liposome-embedded lipid-heme (liposome/li pid-heme) solution was mixed with a red blood cell suspension or myoglobin solution. The oxygen exchange between the two media was measured by visible spectroscopy. It was found that oxygen was provided from liposome/lipid-heme to red blood cell or myoglobin. The exchange percentages agreed with the curves calculated from the oxygen-binding versus-dissociation relationship.

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Photoreduction of viologens by the irradiation of the system containing triethanolamine (TEA), zinc meso-tetraphenylporphyrintrisulfonate ([Zn-TPPS₃]^3-), and viologen has been investigated in the presence of surfactant micelles. In the presence of either cationic or anionic micelles, a remarkable increase in the accumulation of the reduced form of viologen was observed. The existence of the micelles depressed both the quenching rate of the photoexcited [Zn-TPPS₃]^3- by viologen and the reverse reaction rate, recombination rate of the oxidized [Zn-TPPS₃]^3- and the reduced viologen. Comparison between the two reactions has revealed that the recombination rate strongly affects the viologen reduction rate. The effect of the micelles was explained by the electrostatic interaction among the charges of the micellar surface, [Zn-TPPS₃]^3- and viologen.

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Resonance Raman(RR) spectra have been measured for various metallo-trans-octaethylchlorin (M(OEC)) to elucidate the characteristic feature of metallochlorin RR spectra and to provide further insight into chlorin chemistry. The RR spectral characteristics of metallochlorins in comparison with metalloporphyrins explored in this paper are summarized as follows: (i) polarization properties of RR bands of M(OEC) can be interpreted by assuming that M(OEC) has an effective symmetry of C2_2v; (ii) The frequencies of bands in the 1700'1450 cm^-1 region of M(OEC) depend on the metal species coordinated and straight lines are obtained between the frequencies and the transition energy of the Q band; (iii) vibrational properties of ν₁₉ and ν₃ modes are considerably different between M(OEP) and M(OEC); (iv)most of the RR bands in the 1400-1000 cm^-1 region of M(OEC) show pronounced intensity enhancement upon excitation near the Q band, suggesting that electronic excitation in the Q band region involves appreciable stretch of the C_αC_β and C_αN bonds for M(OEC).

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Bacteriochlorophyll(BChl) c was extracted from Chloroflexus aurantiacus and purified by reversed-phase HPLC. This pigment consists of a complex mixture of homologues, the major component of which was characterized by NMR and mass spectroscopy. Unlike p reviously characterized BChls c, the pigment from C. aurantiacus is a racemic mixture of R. and S-isomer with different configurations at the 2 a chiral center.

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Resonance Raman (Fig.1) and infrared spectra of intact and metal-substituted chlorophyll a have been observed in solution. Some band series have been found to be metal-sensitive, and the vibrational frequencies (ν) of these metal-sensitive bands are inversely correlated (Fig.2) with the Ct-N distance (d), where Ct is the center of the chlorin ring and N is the nitrogen atom in the pyrrole ring. To express this relationship, a simple equation, ν=K(d_r-d)-ν_r, is proposed. In this expression, the d value of the porphyrin w ith least strain (a reference porphyrin) is given by d_r, and we assume that d_r is equal to 2.010 Å. The vr value corresponding to this reference porphyrin and parameter K can be calculated from the observed data. Using the above equation, some analogies are found between the vibrational frequencies of chlorophyll α and those of metal-octaethylchlorin (Table 1),

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In the photoinduced hydrogen evolution with a four-component (electron donor-photosensitizerelectron carrier-catalyst) system, the charge separation step between the photoexcited sensitizer and electron carrier is one of the most important processes. As methylviologen (electron carrier) is complexed with [Zn-TPPS₃]^3- photosensitizer and the comp lex is inactive as a photosensitizer, the effective concentration of the photosensitizer decreases. When various bipyridinium compounds are used as electron carriers, some bipyridinum compounds are complexed with [Zn-TPPS₃]^3- to a smaller extent and the higher photoinduced hydrogen evolution rates are observed.

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A mixture of amino acids and glycerol were analyzed by means of fast atom bombardment (FAB) mass spectrometry and tandem mass spectrometry (TMS). Affinity of various metal ions (Li, Na, K, Rb, Cs, Mg, Ca, Al) with amino acids and glycerol were studied. In the cases of leucine(Leu) and Isoleucine(tle) in a matrix of glycerol(G) and a dditives such as alkali metal chlorides (AX=LiCl, NaCl, KCl, RbCl, CsCl), precursor ions (Leu+A)⁺ and (Leu+G+A)⁺, were measured by the second mass spectrometer. The collisionally activated decomposition (CAD) spectra of (Leu+A)⁺, in the presence of LiC1, showed complex fragmentation.

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Stereoselectivities for the complex formation between copper(II) and diastereomeric tripeptides with two leucyl and one glycyl residues, and hydrophobic interactions between, the side chains in the complexes have been studied by potentiometric titration and circular diclirosrn (CD) methods. The complexes containing the Leu-Leu moiety of the same chirality, e. g. Cu(_L-Leu-_L-Leu-Gly), are more stable than those with different chirality, e. g. Cu(_L-Leu-_D-Leu-Gly). But, when the two leucyl residues are separated by one glycyl residue, the stereoselectivity is not observed. The stereoselection takes place in the step of ionization of the amide hydrogen between the two leucyl residues. The hydrophobic interactions between the side chains have been estimated from the additivity of the CD magnitude in the d→dt ransition band of copper(II).

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One of us recently reported the development a novel epimerization reaction of the aldohexose that proceeds immediately and smoothly under mild conditions. This reaction system consists of metal, alkylenediamine derivatives, methanol and aldohexose as a substrate. Various kinds of N-alkyl-substituted ethylenediamine derivatives were prepared to study the effects of ligand on the epimerization. The introduction of more hydrophobic long alkyl group on N atom affects the amphibility of the complex which plays an important role in the epimerization.
Among the various kinds of ligands, N, N'-dialkylethylenediamine showed the highest activity for C-2 epimerization of glucose and mannose. Using this reaction system, the epimerization attained equilibrium in a few minutes under mild conditions. The equilibrium position between the C-2 epimers could be shifted forward glucose side by using the more hydrophobic ligand. It was confirmed that this catalytic epimerization proceeds more effectively, if N, N'dialkylethylenediamines containing more hydrophobic long N-alkyl substituents were used as a ligand. The introduction of hydrophobic alkyl group to N atom makes the reaction field more amphiphilic, and affects the solubility of the ligands. The conversion was proportional to the reaction temperature which have an influence upon the solubility of the nickel-diamine complexes.

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Dimethyl(2, 4-pentanedionato)gold(III)[1] reacts with adenine(Ade) and cytosine(Cyt) to give nucleobase-chelated square planar dimethylgold(III) complexes [AuMe₂(Nuc-H⁺)]_n(Nuc=Ade, Cyt), liberating the quantitative yields of 2, 4-pentanedione in dimethyl sulfoxide at room temperature. The reactions of [1] with various nucleosides such as adenosine (Ado), cytidine(Cyd), and guanosine(Guo), also give reversively equilibrium mixtu res of similar square planar dimethylgold(III) complexes. having a chelating nucleoside ligand. The - deprotonation positions in the nucleobases are N(9) and N(1) for Ade and Cyt, and those in the nucleosides are NH₂ for Ado and Cyd and N(1) for Guo, respectively. The possible stru ctures of those complexes are presented on the basis of their NMR spectra.

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cis-Diamminedichloroplatinum(II) complex (cis-DDP) is widely utilized as an anticancer agent for clinical treatments of various cancers. It has been repeatedly confirmed that cis-DDP binds specifically to DNA in cancer cells to inhibit the replication of the DNA. Therefore, many investigations have been made concerning novel platinum complexes with various carrier ligands to be used as anticancer agents. However, the studies on the plantinum group complexes coordinated with a ligand containing sulfur atoms have not been reported yet. In this paper, tiovel platinum group complexes, dichloro(2-aminoethylsulfonyl)platinum (II) and dichloro(2-aminoethylsulfonyl)palladium(II), were synthesized. The investigations were also carried out on the cytostatic-cytotoxic activities, the interactions between the platinum group complexes and DNA, as well as DNA constituent nucleosides by analyzing the UV spectra, UV difference spectra and the liberation concentration of the chloride ions from the platinum group complexes. The palladium complex was found to exhibit a specific cytostatic-cytotoxic activity, as well as the platinum complex. In the interactions of the platinum group complexes with DNA and the nucleosides, the platinum complex was suggested to be specifically different from the palladium complex in its binding to nucleosides.

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Absorption and circular dichroism (CD) spectra of the solutions containing [Mo₂^vO₄(H₂O)₆]²⁺ and nucleotides (nucleoside 5'-phosphates) such as ATP, ADP, AMP, GTP, CTP, and ITP, were measured over a pH range 1-11. Those with adenosine and ribose-5-monophosphate were also studied. Spectral data (Fig. Table 1) indicate that the triphosphates interact with the Mo^v throughout the pH range studied. In acidic solutions, the nucleotides coordinate to Mo^v with the phosphate site. In basic solutions, however, both phosphate and base participate in the coordination to Mo^v. Interaction with sugar moiety is also indicated in strongly basic solutions. Di- and monophosphates interact similarly to the triphosphates in basic solutions, but cause precipitates in acidic solutions.

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To obtain structural information of ternary metal complexes involving nucleotides and aromatic amines as a model for enzyme-metal ion-nucleotide interactions in the active center of the enzymes, crystal structures of the three compounds were determined by X-ray diffraction methods. The target compounds are [Cu(AMPH)(phen)(H₂O)]₂·(NO₃)₂·8H₂O [1](AMPH=N(1)-protonated adenosine 5'-monophosphate and phen =1, 10-phenanthroline), [Cu(GMP)(dpa)(H₂O)]₂·3H₂O [2] (GMP=guanosine 5'-monophosph ate and dpa=di-2PYridylamine), and [Cu(dUMP)(dpa)(H₂O)]₂·5H₂O [3] (dUMP=uridine 2'-deoxy-5'-monophosphate).

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The stability constants, K, of titled mixed ligand complexes with N-unidentate amino acidates were determined spectrometrically in mixed solvent of DMF and water (1: 4) at 20°C. The K values increased in the order of asparagine(2.8 x10²)<serine<alanine<phenylalanine<valine<leucine<NH₃<tryptophan(7.9x10³), and show ed a small difference in the optical form of amino acidates. In order to explain the order of the stability, hydrophobic interactions between the side chain of amino acidate and the aromatic ring of the Schiff base ligand were proposed.

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Relationship between physiological roles of essential trace metal ions and their valence states was studied by ESR spectroscopy on plant leaves. The ESR spectra of leaves of Radish (Kaiware daikon, Raphanus sativus Linne), which were cultivated in the presence of various metal ions such as Mn²⁺, VO₃^-, VO²⁺, Cu²⁺, Co²⁺ and Ni²⁺, were directly measured at 77 K from immediately after the cutting-down of the leaves to the 16 th d. ESR signal levels due to Mn(II) and V(IV) (vanadyl form) in raw leaves changed with drying-up after the harvesting of the leaves.

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The role of bivalent metal cations in the cyclization of acyclic allylic diphosphates to cyclic monoterpenoids was investigated. The reaction of linalyl diphosphate (LPP) with the bivalent metal ions was found to give much more amount of a-terpineol than in the cases of neryl diphosphate (NPP) and gerany diphosphate (GPP) with the metal ions. The reaction of these allylic diphosphates with Mn²⁺ ion was traced by the ¹H-NMR spectroscopy, and a change in the intensity of the C-9 methyl proton signal was observed only in the case of LPP. This change was found to result from the coordination of Mn²⁺ ion with the diphosphate moiety. The structure analysis pf LPP chelated with Mn²⁺ ion was carried out by CNDO/2 calculation, and the analysis indicated that the C-0 bond of LPP is weakened by the chelation of Mn²⁺ ion.
It was thus establishe d that the bivalent metal cation chelates the diphosphate moiety of LPP and plays a role in the production of linalyl cation by pulling out the diphosphate moiety.

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The cation-exchange characteristics for Ca2+ ions in synthetic hydroxyapatites (HAP) [Ca₁₀(PO₄)₆(OH)₂] and 2 B group ions (Zn²⁺, Cd²⁺ and Hg²⁺ ions) in aqueous solutions containing various counter anions (Cl^- and NO₃^- ions) have been investigated by a normal batch method at 25°C; the influence of H⁺ ions on these characteristics was determined.

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Ethylene and carbon monoxide complexes of copper(I)were synthesized as a model for the ethylene receptor site of plants. Spectroscopical characterization was made on the complexes of the formulation of [Cu(tmi)I., ]ClO₄ and [Cu(bmi)L]ClO₄(L=C₂H₄ and CO), where TMI and BMI are tris(1-methyl-2-imidazolyl)methanol and 1, 1-bis(1-methyl-2-imidazoly)-1-octanol, respectively. The ¹H-NMR signal of the ethylene protons of [Cu(tmi)(C₂H₄)]ClO₄ [1] is O.52 ppm upfield from that of free ethylene.

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NMR spectroscopy of ³¹P and ²⁵Mg is applied to a study of conformation of Mg²⁺ binding to ATP and Mg²⁺ interactions with ATP.³¹PP-NMR chemical shifts δ and rates R₁ of longitudinal magnetization recovery (LMR) were measured as a function of temperature between 0°C and 45°C for some ratios R of Mg²⁺ to ATP. ²⁵Mg-NMR spectra were obtained for 0≤R≤10 at room temperature at a constant Mg²⁺ concentration of 25 mmol·dm^-3 with vario us ATP concentrations.

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Previously we found that oxovanadium(IV) ion (vanady1(IV) ion) (+4 oxidation state) was detectable in subcellular fractions of rat liver after i. p. injection of vanadate (+5 oxidation state) ion. Since glutathione (GSH) is present at as high a concentration as 3-5 mmole·dm-³ⁱn most tissues, vanadate may presumably be reduced to oxovanadium by GSH, which is a candidate of endogenous reducing compound. This paper reports the characterization of the GSH-, penicillamine (Pen)-, cysteine (Cys)- and thioglycolic acid (TGA)-oxovanadium(IV)complexes over a wide pH range on the basis of results of potentiometric titrations, optical, ESR and ¹³C-NMR spectrometries as well as the reductive complex formation between GSH and vanadate.

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A variety of open-chain oligo(oxyethylene) ethers and alkanoic acids were employed as carriers to examine the active and competitive transport of alkali (M⁺: Li⁺, Na⁺, and K⁺)and alkaline earth (M²⁺ Mg²⁺, Ca²⁺, and Ba²⁺) metal cations in a chloroform liquid membrane system. Only when the combination of appropriate oligoether and alkanoic acid was used, efficient transport of cations except Li⁺ and Mg²⁺ was carried out, indicating the cooperative action of the two components in these systems. K⁺ and Ba²⁺ were preferentially transported in most of the M⁺ and M²⁺ competitive systems, respectively. The efficiencies of M²⁺ transport were generally higher than those of M⁺ with the same cooperative carrier.

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A kinetic ESR study for copper ion transport. was done by using a liposomal membrane containing a surfactant azacrown ether of 3-dodecyl-1, 5, 8, 12-tetraazacyclotetradecane-2, 4dione (DD 14 N 4). Time-resolved ESR measurements for the metal incorporation were carried out by mixing a copper tetraglycine complex solution with the liposome suspension. In the earlier reaction stage, the ESR mainly observed is the isotropic one.

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We prepared platinum(W) complexes containing 1, 2-cyclohexanediamine (=dach) or 2(aminomethyl)cyclohexylamine -(=amcha) as a carrier ligand in order to increase water-solubility of the corresponding Pt(II) complexes. Their antitumor, activity was tested against murine leukemia L 1210, and almost all of the Pt(IV) complexes tested were antitumor active. Dach Pt(IV) complexes showed higher antitumor activity than amcha Pt(IV) complexes and among the former complexes, Pt(IV) complexes containing l-dach exhibited higher activity than those of other dach isomers, i. e., meso-and d-dach. Especially, trans-PtCl₂(oxalato)(l-dach), trans-PtCl₂(malonato) (l-dach) and trans-PtCl₂(oxalato)(dl-trans-am cha) exhibited excellent antitumor activity.

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cis-Diamminedichloroplatinum (II) (DDP) is a useful antitumor platinum complex. Aiming at reducing its severe nephrotoxicity, a number of platinum complexes were synthesized and their antitumor activity was studied. As a result, the degree of antitumor activity as well as antitumor spectrum of platinum complexes seemed to depend on the nature of carrier ligand, while the leaving group influenced the solubility, stability and toxicity.

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