An overview of the crystal growth of organic molecular complexes which include organic metals snd superconductors is presented. Organic molecular complexes are classified into several groups (mainy proton-transfer and charge-transfer type) according to the intermolecular interactions of component materials. All organic conductors so far known are of charge-transfer type. They are prepared by the redox reactions such as i) a direct reaction of donor and acceptor in gas, liquid or solid phases, ii) metathesis, and iii) electrocrystallization. Several examples of the crystal growth of conducting organic compounds prepared by these redox methods are described.
Organic nonlinear optical materials have recently attracted high attention because of their superior properties such as larger susceptibility, faster response, multiplicity in morecular and aggregating structures, compared with those of inorganic and semiconductiong substances so far elucidated. In the first, various nonlinear optical effects and their applications are explained. Thereafter, pioneering achievements of opto-electronic properties are summarized. A recent trend in progress and future perspective of the relevant fields are also presented in view of molecular engineering, crystal engineering and morphological engineering, with particular reference to crystallography and crystal growth.
Melt growth of organic single crystals for nonlinear optical application is reviewed briefly, compared with that of inorganic crystals. The Bridgeman and Czochralski growth of 2-methyl-4-nitroaniline (MNA) single crystal which has extremely large nonlinear optical coefficients are described. Growth conditions of transparent and sizable MNA single crystal and origin of difficulties in melt growth, such as coloring, subgrain and fiber-like growth, discussed. It is shown that melt growth of large organic bulk crystal with opical quality is possible as well as that of inorganic crystals, but significant progrss in skill needs to be made in the present growth technique for nonlinear optical application.
The material which is optically active and chiral with no inversion symmetry, has a high possibility to be employed as a nonlinear optical device for a second harmonic generation. In addition, the crystals of this kind may reveal a good optical transparency of blue or ultraviolet light. Larginine phosphate monohydrate (LAP) is a promising organic crystal for higherorder harmonic generator of high power lasers. The large single crystals of LAP and deutrated LAP (DLAP) were grown in the present study. Optical and laser properties of transmission, phase matching angles, and a nonlinear optical coefficient were measured. Conclusively, the experimental data indicated that LAP and DLAP can be used, like KDP, in high power lasers.
A review is given on the crystal growth of hen egg-white lysozyme. The history, principle, and technique of protein crystal growth are first briefly described. It is then shown that the crystal growth of lysozyme is similar to that of lower molecular weight substances in that (1) the crystal solubility (Cs) can experimentally be determined, (2) a variation of Cs can be represented in phase diagrams, and (3) both the size and the period needed for the appearance of crystals (D) are largely determined by the degree of supersaturation. However, lysozyme crystal growth is characteristic in that (1) polymorphism depending on pH, counterion, and temperature is observed, (2) the number of tetragonal crystals increases on reducing the degree of supersaturation below a certain value, leading to smaller crystal size, and (3) both D and the crystal growth rate are much longer than those usually observed for smaller substances.
Recent developments in gene-engineering and protein purification techniques made it possible to get large amount (say 100 mg) of "physrologrcally active proteins", which play important roles in regulating various biological phenomena, but exist very small amount in natural organisms. These technical trends made feasible various physico-chemical studies of such proteins, including crystallization for X-ray structure analyses. Here, our own experiences on the two types of crystals ofhuman recombinant interleukin-2 (IL-2) are described with special emphases on crystallization conditions, such as supersaturation, pH and nucleation, and crystal growth. Brief descriptions are also given to crystal-lizations of some other proteins, namely interferon-β (IFN-β), tumor necrosis factor (TNF) and epidermal growth factor (EGF).
This article reviews polymorphism and impurity effect in the crystallization of amino acids, particularly L-glutamic acid. It is shown that the precipitation process of a and β polymorphs of L-glutamic acid is composed of four steps including a solution-mediated transformation. The predominant effect of the temperature on the nucleation process of the polymorphs is also indicated. As to the impurity effects, it is presented that amino acids such as L-leucine, L-phenylalanine, etc, give rise to the influence on nucleation, crystal growth and transformation processes of the polymorphs of L-grutamic acid. It is also referred that some chiral impurities of amino acids can be used for the optical resolution of the amino acids.
The article reviews recent studies of crystallization processes of polymorphic modifications of lipid molecules, particularly proncipal saturated and mono-cis-unsaturated fatty acids and mixed acid triacylglycerols. Themodynamic and Kinetic aspects of the polymorphic crystallization are discussed in relation to molecular structures, thermal properties with X-ray diffractometry, differential scanning calorimetry and vibrational spectroscopy.
The gallstone formation has been studied from the view point of the reverse process which is solubilization mechanism of gallstones in bile. We employed two bile salts (chenodeoxycholate, ursodeoxycholate) in our experiments, because chenodeoxycholate can solubilize cholesterol well and in contrast, ursodeoxycholate poorly in their micellar solutions. The studies lead us to conclude that bile salt micelles play the major role in chenodeoxy-cholate-rich bile, while lecithin (PC) bilayer vesicles are instrumental in ursodeoxycholate-rich bile, in dissolving processes of cholesterol. When the cholesterol concentration exceeded its solubility limit in the bile salts and PC mixed micellar solution, cholesterol were solubilized by the following mechanisms in bile. a) Excess PC is arranged in an orderly fashion in the aqueous solution since the surrounding of surfactants is bile salts.
The deposition of calcium pyrophosphate dihydrate (CPPD) and hydroxyapatite (HAP) crystals in human cervical ligamentum flavum is described. Specimens of the ligamenta flava were studied by scanning electron microscopy, energy dispersive X-ray microanalysis, and an X-ray diffraction study was carried out on the crystals. It was revealed that small foci of calcification were made of extremely small CPPD plate-shaped crystals. On the other hand, big foci were composed of two chemical species, CPPD and HAP, the latter being encased by the former. The X-ray diffraction pattern of CPPD crystal formed in ligamentum flavum coincided well with that of CPPD already reported (triclinic, P1, a=7.37A, b=8.29A, c=6.61A, a=102.96°, β=72.73°, γ=95.01°, Z=2).
An output stabilizer of r.f. generator was developed for the preparation of single crystals by floating zone method. The stablizer consisted mainly of a micro-computer and two digital voltmeters. The voltmeters were used for measurements of the anode voltage and the r.f. current. The anode voltage was controlled by feed back, using the computer. The stability of r.f. current consequently increased by one order of magnitude (0.03%).