Masanao Oya

Biodegradable implant composites for local therapy

Abstract Implantable polymer-drug composites prepared by radiation polymerization have been applied to cancer therapy. Local chemotherapeutic treatment can be achieved by te use of implantable needles and buttons consisting of polymer and various anticancer agents. For example, the luteinizing hormone releasing hormone (LHRH) agonist-polymer needles have been successfully used for the hormone therapy of prostatic organ cancers. The effects of chemical structure on the in vivo degradation and controlled release were studied for biodegradable polymers of polypeptides, poly(α-hydroxy acids) and polydepsipeptides.

Fusibility of Poly(N-carboxy α-Amino Acid Anhydride) Materials Treated under Pressure-Heat Conditions and in Vitro-in Vivo Degradation of Hot-Pressed Materials

Abstract Powdered poly(N-carboxy α-amino acid anhydride) materials were treated at temperatures of 50, 100, 150, and 200°C under a pressure of 150 kg/cm2. A number of hot-pressed materials showed simultaneous fusion and contraction in volume. The fusion temperature of the hot-pressed materials was generally lower than the true melting point of the powdered materials at atmospheric pressure (determined with a Differential Scanning Calorimeter). The hot-pressed materials had high rigidity and transparency. The in vitro-in vivo degradation of hot-pressed materials was also investigated. The homo- and copoly(α-amino acid) materials used in this study were scarcely degraded, though debenzylated t e rpolymers such as β-benzyl-L-aspartate/aspartic acid/L-leucine and γ -benzyl-L- glutamate/glutamic acid/L - leucine we re significantly degraded in both the in vitro and in vivo experiments. It was found that the in vivo degradation profile of hot-pressed terpolymer materials corresponds relatively well to degradati...

A proton nuclear magnetic resonance study on the solution structure of crotamine

Proton nuclear magnetic resonance (NMR) spectra of crotamine, a myotoxic protein from a Brazilian rattlesnake (Crotalus durissus terrificus), have been analyzed. All the aromatic proton resonances have been assigned to amino acid types, and those from Tyr-1, Phe-12, and Phe-25 to the individual residues. ThepH dependence of the chemical shifts of the aromatic proton resonances indicates that Tyr-1 and one of the two histidines (His-5 or His-10) are in close proximity. A conformational transition takes place at acidicpH, together with immobilization of Met-28 and His-5 or His-10. Two sets of proton resonances have been observed for He-17 and His-5 or His-10, which suggests the presence of two structural states for the crotamine molecule in solution.

Preparation and properties of copoly(n-hydroxyalkyl-d,l-glutamine) membranes

Abstract Random copolypeptide (PHADLG) membranes consisting of N-hydroxyalkyl- d -glutamine (HADG) and N-hydroxylalkyl- l -glutamine (HALG) covering the whole range of d,l -copolymer composition were prepared by carrying out aminolysis reactions with 3-amino-1-propanol (P) or 5-amino-1-pentanol (Pe), together with a crosslinking reaction with 1,8-octamethylenediamine (OMDA) on membranes of the starting random copolymers (PBDLG) consisting of γ-benzyl- d -glutamate and γ-benzyl- l -glutamate. The relationships between their bulk structure and membrane properties were investigated, such as the swelling ratio in water, tensile properties, water vapour permeability, and enzymatic degradation behaviour of the membranes in a pseudo-extracellular fluid (PECF), as a function of d,l -copolymer composition. The tensile properties of d,l -copolymer membranes were highly dependent on the swelling ratio of PECF. Biodegradation of these membranes in vitro by papain indicated that degradation was a bulk rather than a surface phenomenon, and that the rate of degradation of membranes was also highly dependent on the hydrophobicity of side chains, d,l -copolymer composition as well as on the swelling ratios of the d,l -copolymer samples.

Conformational changes of a mitochondrial precursor protein on binding to phospholipid vesicles and SDS micelles: a circular dichroism and fluorescence spectroscopy study

Conformations of an artificial mitochondrial precursor protein pCox IV‐DHFR have been analyzed by CD and fluorescence spectroscopy in the presence of (cardiolipin‐rich) phospholipid vesicles or SDS micelles. Binding of pCox IV‐DHFR to phospholipid vesicles involves a conformational change, which is presequence‐dependent, accompanies alteration in the secondary structure of the DHFR moiety, but is different from total unfolding of the polypeptide chain. On the other hand, a conformational change of the fusion protein on binding to the micelles of a positively charged detergent, SDS, is not presequence‐dependent.

Step-wise thermal denaturation of cobrotoxin, a snake venom neurotoxin from Naja naja atra: a proton nuclear magnetic resonance study

Temperature dependence of proton nuclear magnetic resonance spectra has been followed for cobrotoxin, a postsynaptic neurotoxin fromNaja naja atra venom. Several aromatic amino-acid residues, including the functionally essential Trp-29 located at the tip of the central loop of the molecule, have been found to undergo a thermal structural transition above the global thermal denaturation temperature. It is suggested that a local structure around these residues behaves somehow independently of the rest of the molecule, and that such structural organization may be favorable for a conformational change of a neurotoxin molecule on binding to acetylcholine receptor.

State of functionally essential Trp-29 in snake venom neurotoxins: a proton nuclear magnetic resonance study

Proton nuclear magnetic resonance (NMR) spectra have been recorded of various neurotoxins from snake venoms.pH dependence of the chemical shifts and resonance intensity has been followed for the functionally essential Trp-29. The indole N-1 proton of Trp-29 in α-bungarotoxin, toxin B, and cobrotoxin exhibits appreciably large upfield shifts as thepH is lowered and the suppressed exchange with the solvent hydrogen atpH 3–4, but not inNaja haje annulifera 10 where Asp-31 is replaced with Gly-31. This observation strongly suggests the presence of a hydrogen bond between Trp-29 and Asp-31 that is probably important in stabilizing the arrangement of the functionally essential residues to form a distinct binding region for the receptor.

Proton NMR resonance assignments and surface accessibility of tryptophan residues of a dimeric phospholipase A2 from Trimeresurus flavoviridis

Proton NMR spectra of a dimeric phospholipase A2 from Trimeresurus flavoviridis have been recorded. N‐1 proton resonances of the tryptophan indole rings have been detected and assigned to specific positions, Trp‐3/Trp‐30, Trp‐68 and Trp‐108, by comparing the spectra of the enzyme derivatives with tryptophans oxidized to differing extents. Photo‐CIDNP experiments have revealed that Trp‐68 and Trp‐108 are exposed while Trp‐3 and Trp‐30 are buried in the molecule. This is consistent with the X‐ray crystal structure of a homologous phospholipase A2 from Crotalus atrox where residues 3 and 30 are located at a dimer interface, but inconsistent with the results of stepwise oxidation of tryptophan residues.

Adsorption of Organic Posphorous Insecticides and Herbicides by Polyamino Acids.

Recently, it have been reported that many clinical cases have injested insecticides and herbicides either for the purpose of suicide or by mistake, and thet these agricaltural chemicals poison the soil, especially rivers or lakes. Removal of these compounds is thus needed. In this regard, we report herein the application of polyamino acids for the adsorption of these agricultural chemicals by using the quartz-crystal microbalance (QCM) method.The homopolyamino acids exhigbit a high affinity to malathion. Poly (Leu) adsorbed an equal mass of cyanophos and trifluralin. Accordingly, polyamino acids are expected to be useful as adsorbents for organic phosphorous insecticides and herbicides.

Conformational Transition of Copolypeptides with both Hydrophilic and Hydrophobic Groups Side Chains.

側鎖に塩基性親水基を持つリジソ,オルニチソと疎水性基をもつアラニン,α -アミノ酪酸,さらにヒドロキシル基を持つセリンとのコポリペプチドを合成し,各種緩衝液中でpHおよび共存イオンのポリペプチドの二次構造に与える影響を,円偏光二色性スペクトルを用いて検討した.また,ポリリジンPoly(Lys)とも比較検討した.リジン-アラニン共重合体Poly(Lys,Ala)はクエン酸ナトリウム緩衝液中(pH4.53)でらせん(ヘリックス)構造をとるのに対し,塩化カリウム系(pH6.25)ではコイル状であった.また,リン酸緩衝液(pH6.86)ではPoly(Lys,Ala)共重合体はヘリックス構造をとるのに対しPoly(Lys)はコイル状であった.また,Poly(Lys,Ser)はヘリックス構造をとりにくいなど,ポリペプチドの二次構造は,溶液中の陰イオンの種類と構成するアミノ酸の種類に大きく依存した.側鎖にカルボキシル基とメチル基を有するアスパラギン酸-アラニン共重合体についても合わせて検討を行った.