Proteins are usually in an equilibrium between the folded and the unfolded state. Therefore, for the stabilization of proteins against reversible denaturation, the free energy change for the unfolding should be increased by stabilizing the folded state by lowering the energy level of the folded state or by destabilizing the unfolded state by raising the energy level of the unfolded state. On the other hand, various processes can be coupled with the unfolded state of proteins. For example, protease digestion of proteins at physiological temperature may be one of such processes. The process would lead to an irreversible denaturation. For the stabilization of proteins against the irreversible denaturation coupled with the unfolded state, a kinetic stabilization is important, that is, the activation free energy for the unfolding should be increased. Methods for the kinetic stabilization were discussed. Finally, the irreversible chemical deterioration of proteins was considered.
In this review, our novel research works in both low temperature plasma chemistry and solid state plasma chemistry were described. As for low temperature plasma, the ESR study on plasma-induced radicals of several selected conventional polymers was shown including the detailed analyses of the radical structure and the mechanism by which the radicals were formed on typical degradable methacrylic polymers and crosslinkable polystyrene. One of the pharmaceutical applications of the plasma processing for drug delivery system (DDS) was also described, whcih includes the preparations of double-compressed tablet consisting of drugs as a core material and various types of polymers as a wall material followed by plasma-irradiation on such a tablet. As for solid state plasma, the detailed reaction mechanism of solid state mechanochemical polymerization was shown including the solid state single electron transfer and the special feature of the resulting polymers. The structural criteria for polymerizable monomer derived from the quantum chemical considerations were also established. Based on the above findings, we synthesized various polymeric prodrugs by mechanochemical polymerization and studied the nature of hydrolyses (drug release).
Nerve growth factor (NGF) is a polypeptide that is necessary for the survival and growth of developing sympathetic and sensory neurons as well as basal forebrain cholinergic neurons in the brain. The effects of NGF are mediated by the binding of the factor to its specific receptor present on the surface of NGF-responsive cells. Since NGF-responsive basal forebrain cholinergic neurons are lost in Alzheimer's disease, treatment with NGF may be therapeutically beneficial for the patients with this disease. Our studies were focused on the purification, amino acid sequence, enzyme immunoassay (EIA), NGF-biosynthesizing cells, regulation of the biosynthesis, compounds stimulating NGF-biosynthesis/secretion, etc. The major results obtained are summarized as follows : 1) We purified NGFs from snake venoms and determined their amino acid sequences. Among them, Crotalus adamanteus- and Vipera russelli-NGFs were glycoproteins. 2) We developed highly sensitive (0.03-0.05 pg/tube or bead), simple, and reliable EIA systems for NGFs and NT-3. 3) Catecholamine, its derivatives, p-quinone derivatives, nicotine, nicotine derivatives, coenzymes, etc. enhanced the NGF-biosynthesis/secretion of fibroblasts and astrocytes by increasing their cellular content of NGF mRNA. 4) Basal forebrain-lesioned rats (an animal model of amnesia) administered 6-(4-hydroxybutyl)-2, 3, 5-trimethyl-1, 4-benzoquinone (TMQ) orally showed improvement not only their NGF level and choline acetyltransferase (CAT) activity in the brain but also their memory and learning. 5) Interleukins (IL)-4 and -5 significantly increased the amounts of NGF secreted by mouse astrocytes ; whereas IL-2, -3, and -6 had no significant effect. 6) Interferons-β and -γ inhibited the DNA- and NGF-synthesis in growing astrocytes cultured from neonatal mouse brain but they had no effect on the NGF-synthesis/secretion in quiescent astrocytes. 7) Alkylcatechols regulated the NGF gene expression in astrocytes via both protein kinase C- and cAMP-independent mechanisms.
The elucidation for the mechanism of receptor-mediated signal transduction has been the aim of our extensive studies. Cyclic AMP, which was controled by membrane adenylyl cyclase, was an intracellular signal (the first second messenger in cells proposed by Sutherland) given by hormones and neurotransmitters. The GTP-binding (G) proteins play an important role in communication between membrane receptors and the adenylyl cyclase catalytic unit. One (Gs) of the G proteins is involved in the activation, while the other (Gi) is involved in the inhibition of adenylyl cylase. Islet-activating protein (IAP, pertussis toxin, PTX) catalyses the transfer of the ADP-ribose moiety of NAD to the a subunit of Gi, resulting in a complete loss of the Gi functions. In some cases, arachidonic acid (AA) regulates cell functions as a second messenger. AA serves as a precursor to a number of biologically active lipids including prostaglandins and leukotrienes. Activation of cell surface receptors of many cell types results in the release of AA from membrane phospholipids by phospholipase A2 (PLA2). A new family of PLA2 has been discovered in the cytosol of various cells. The activation of receptor-mediated AA release by cytosolic PLA2 was also regulated by PTX-sensitive G proteins. PTX treatment inhibited cell growth of fibroblasts by serum and growth factors. G proteins have been involved in receptor-receptor interactions in neuronal cells. These findings suggest the regulatory roles of cell surface receptors-coupled G proteins in signal transductions and cell functions.
Effects of the oral or intraperitoneal administration of an Enterococcus preparation, FK-23, to mice on the interferon (IFN) production by their spleen cells and on the host defense against the infection with herpes simplex virus (HSV)-1 were examined. Spleen cells were obtained from the mice intraperitoneally treated with cyclophosphamide (CY) and subsequently orally administered FK-23 preparation, and then cultured with phytohemagglutinin-P or bacterial lipopolysaccharide in vitro. They produced higher titers IFN than those obtained from control mice which were not treated with the FK-23 preparation. The IFN activity was neutralized mainly by antiIFN-β antibody. Correspondingly, oral (5mg/mouse) or intraperitoneal (1mg/mouse) administration of the FK-23 preparation protected some of the CY-pretreated mice from death by HSV-1 infection.
A simple, rapid and convenient chromatographic method, which permits the simultaneous determination of chlorpheniramine (CP) and maleate (MA), recently developed by the authors was applied to the analysis of chlorpheniramine maleate (CPM) in cough and cold drugs. In this method, a Capcell Pak C8 column and an isocratic mobile phase containing 15% methanol, 50mM KH2PO4 and 5mM tetra-n-butylammonium phosphate as an ion-pair reagent were used. By using the mobile phase adjusted to pH 3.0 with orthophosphoric acid, fumaric acid, MA, CP, acetaminophen (paracetamol), caffeine, and m- and p-hydroxy-benzoic acid as candidates for an internal standard were eluted separately within 17 min. Detection was carried out with UV detector at 215 nm. Under the same conditions, five other antihistamines analogous to CPM were also separated. The calibration graphs for CP and MA showed good linearity in the range of 0.5 -10 nmol (0.195-3.9μg) per 20μl injection, respectively. The proposed method was successfully applied to the simultaneous determination of CP and MA, i.e., CPM analysis, in commercial cough and cold drugs which pharmaceutical forms were tablet, granule and syrups.