大川 祐輔

The characteristics of sol-gel transition of a mixture made by mixing two kinds of gelling agents of different nature, i.e. gelatin and carrageenan were examined. The sample solutions consisted of 3.00 wt % gelatin solution, 1.00 Wt % K-carrageenan solution and 4.00 wt % mixed solution which was prepared by mixing the said gelatin and carrageenan solutions in the ratio 3: 1. In the experiment, the optical rotation and the dynamic viscoelasticity were measured under the same temperature change program. As the sample solutions were cooled, the carrageenan solution started to show a change in the specific rotation in the first place, followed by the mixed solution and finally the gelatin solution. The gelatin and the mixed solutions had the same increasing tendency in the specific rotation, whereas the carrageenan solution changed a little. When the mixed solution was chilled to set, it turned into a highly elastic gel. In the mixed solution, the gelation of carrageenan was found to precede that of gelatin.

Previously gelatins have been shown to reduce copper( II) bis(bipyridine) [CBB(II)] and that only sugars of the reducing substances, which are known to be gelatin impurities, reduced CBB(II). Even using high-performance liquid chromatography with electrochemical detection, in which the column eluent reacted with CBB(II), the reducing substances could not be identified with sugars. In the present paper the reaction rate of gelatins with CBB(II) was measured and compared with that of sugars. The rare constants of gelatins are very close to those of sugars with a hemiacetal structure, but addition of glucose to the second ripening solution for gold sensitization did not result in a significant effect on the photographic characteristics, while addition of glucosamine increased fog. It was concluded that the reducing properties of gelatin are attributed to amino sugars with a hemiacetal structure.

The characteristics of sol-gel transition of a mixture made by mixing two kinds of gelling agents of different nature, i.e. gelatin and carrageenan were examined. The sample solutions consisted of 3.00 wt% gelatin solution, 1.00 wt% κ-carrageenan solution and 4.00 wt% mixed solution which was prepared by mixing the said gelatin and carrageenan solutions in the ratio 3:1. In the experiment, the optical rotation and the dynamic viscoelasticity were measured under the same temperature change program. As the sample solutions were cooled, the carrageenan solution started to show a change in the specific rotation in the first place, followed by the mixed solution and finally the gelatin solution. The gelatin and the mixed solutions had the same increasing tendency in the specific rotation, whereas the carrageenan solution changed a little. When the mixed solution was chilled to set, it turned into a highly elastic gel. In the mixed solution, the gelation of carrageenan was found to precede that of gelatin.

The gel maturation behaviour of aqueous gelatin was studied with dynamic rheometry, optical rotation measurement and differential scanning calorimetry. The gelation conditions were controlled with several temperature programmes focusing on controlling the degree of freedom in molecular motion of the cross-linked sites through thermal agitation. It is demonstrated that the gel maturation proceeds more effectively under conditions with the appropriate degree of freedom. The observed behaviour was interpreted with a model including helix precursor generation and rearrangement from the precursor to an ordered helix.

In order to build an electronic interface between a redox enzyme and an electrode, we have designed a new mediator system, where the mediator molecule is immobilized onto an electrode surface via a long flexible chain-"tethered" mediator. As a prototype tethered mediator system, a ferrocene derivative with a long poly(oxyethylene) chain was immobilized onto an SnO2 electrode and electron mediation function to horseradish peroxidase (HRP) was examined. In the cases of both soluble and co-immobilized HRP, we observed,a catalytic current for hydrogen peroxide reduction. The kinetic analysis exhibited that the tethered ferrocene effectively mediates electron between the enzyme and the electrode. (C) 1999 Elsevier Science S.A. All rights reserved.

An FIA system capable of the direct and simultaneous determination of ascorbic acid and glucose in commercial soft drinks is described. The system features a flow-through electrolysis cell (electrochemical filter, ECF) for a coulometric determination based on the quantitative electrolysis of ascorbic acid and a glucose oxidase monolayer electrode for the amperometric determination of glucose. Although ascorbic acid interferes with the glucose biosensor, quantitative electrooxidation in the ECF supresses the error. The glucose biosensor did not exhibit saturation for 0.1 M-order glucose samples. The measured values for nine commercial soft drinks without any pretreatment, such as dilution, showed a good correlation to those determined with conventional methods.

Changes in the rheological properties of a gelatin solution during gelation were studied. Samples with various concentrations (0.1-6.0 wt%) were cooled from 45 degrees C to 10 degrees C at a constant cooling rate and then kept at 10 degrees C. When the sample was cooled to a certain temperature, the viscosity started to increase. A steep rise in rigidity was observed after the viscosity increase. The value of tan delta of each sample first increased and then decreased and converged to a characteristic value. We can understand this behaviour well in the framework of percolation transition theory. Concentration dependence of the rheological behaviour in the gelation process suggests that the gel structure of < 1.5 wt% samples and that of > 1.5 wt% samples are different. In the higher concentration region, almost all the crosslinking points lake part in the gel network formation, and thus the gels all feature an essentially similar structure. In the lower concentration region, some of the crosslinking points become dangling bonds and do not contribute to rigidity, resulting in a mechanically weak gel network. A 0.1 wt%-order sample, that never gells macroscopically, also showed a rise in rigidity when cooled, suggesting formation of a gel network of infinite size even in this low concentration range.

The influence of the liming period in the manufacturing process on the chemical and photographic properties of gelatin was investigated. Three limed osseins soaked for various periods were prepared and gelatins were extracted from them. The impurity contents of the gelatins and the physical restraining properties decreased with prolonging liming periods. The impurity contents and physical retardance were also relative to the extraction order. The deionization treatment of gelatin decreased the impurity contents and the differences of restraining effect with extraction order. Furthermore, the fractionation of sample gelatins by use of gel permeation chromatography was applied to study the relationship to the molecular weight of impurity contents and amino acid composition, as affected by the liming period.

The authors have already reported the examination of the gelling characteristics of gelatin solution by a thermal sensor method. At solution concentrations below 4%, the gelling process was studied by optical rotatory power measurement. In this paper, the changes of the molecular weight distribution (MWD) in the gelling process during the cooling period were investigated. The MWD of the gelatin solution was measured at the gelling temperature by gel permeation chromatography. The concentration of the gelatin solution was more related to the gelling phenomena than the cooling temperature. Some differences were observed in the changes of MWD among the types of gelatins.

It was attempted to obtain the standard rate constant (k(0)) for the anodic oxidation of Phenidone (P) in physical developers using spectroelectrochemical measurement in which P was oxidized to Phenidone radical (P-.) on a reflective silver electrode and in which the absorbance change owing to the formation and disappearance of P-. was monitored spectrophotometrically. The k(0) obtained in a silver thiocyanate developer was nearly equal to that in the absence of the silver complex (k(0)*) and remained almost constant with time after addition of P, while that obtained in the silver thiosulphate developer was much smaller than k(0)* and increased with time. These results suggested an inhibition of the charge transfer by the adsorption of thiosulphate at the silver surface and a displacement of the inhibiting thiosulphate by a species produced from the P oxidation, for which the inhibiting effect is smaller than that of thiosulphate.

Physical and photographic properties of gelatin depend on the molecular weight distribution of the gelatin, which it is important to control. We controlled the molecular weight distribution of gelatin by pressurizing the sample gelatin solution and jetting it at high velocity from a nozzle to a collision plate. It was found that this method runs effective in controlling the molecular weight distribution of gelatin and in preparing a gelatin which contains mainly alpha and beta components and few high and low molecular weight components.

It is confirmed using spectroelectrochemical measurements that in the presence of gelatin the oxidation product of p-phenylenediamines is consumed to produce a substance which possesses absorption maxima at 340 nm and 500 nm. Gelatin retards the formulation of dye in the coupling reaction. With an amino acid, L-arginine, the observations are similar but move remarkable. It is proposed that the product is an aminated quinonediimine.

本報告では、ゼラチン溶液に超音波を照射することによりゼラチンの分子量分布が変化することについて述べる。使用した振動子の相違によりゼラチンの低分子量化は異なった。超音波照射によるゼラチンの分解機構はゼラチン中の高次構造即ち分子間結合が開裂し、さらにペプチド結合が切断すると推定された。超音波照射によりゼラチンの物性が変化し、写真特性に影響を及ぼすことか明らかとなった。

低濃度のゼラチン溶液を冷却したときの比旋光度の変化を測定してゼラチン溶液のゲル化の過程について考察した。超音波照射処理によって調製した物性の異なるゼラチンを用いて比較検討を行ったところ, 3%以下の濃度ではゼラチンサンプル間に顕著な比旋光度の差は認められず, 冷却時の比旋光度の変化はゼラチンの物性よりむしろ濃度に対する依存性の方が大きかった。アルカリ処理骨ゼラチンを用いて冷却時の比旋光度の増加速度と濃度の関係について検討を行った結果, 冷却の初期において1.5%以上の濃度では比旋光度の増加速度は凡そ2次の濃度依存性を示した。しかし1.0%以下の濃度では1次に近く, 分子間の結合が減り, 分子内におけるコラーゲンフォールドを形成するような構造を生じている可能性が示唆された。1～2%の濃度において, 比旋光度の増加速度の温度依存性を検討し, 低濃度におけるゲル化の活性化エネルギーを求めた。

Gel permeation chromatography (GPC) and temperature solubility were used to isolate different molecular weight fractions of several photographic gelatins. The dependence of the amino acid composition of impurities and metal ion contents on molecular weight was investigated. The lower molecular weight fraction had an unusual amino acid composition. The difference in amino acid composition was observed according to the raw material species, the methods of manufacture and those of fractionation. This lower molecular weight fraction contained more tyrosine, histidine, methionine, hydroxylysine and hydrophobic amino acids than the original gelatin, while it contained less lysine, alanine and acidic amino acids than the original gelatin. It was considered that the low molecular weight fraction contained a certain amount of telopeptide, peptide from the alpha 2 (1) chain and noncollagenous proteins. High contents of iron and calcium ions as impurities were observed in higher and lower molecular weight fractions.

In order to study the relationship between the gelling characteristics and the physical properties of gelatin, five gelatin samples having different properties were prepared by ultrasonic wave irradiation of the original gelatin. The setting times of these modified gelatins were measured by means of the thermal sensor method. The empirical expression (1), which was previously obtained from the setting time I (t), the concentration of the gelatin solution (C) and the cooling temperature (T) was applied to study the gelling characteristics of gelatin. t = a .(T/C) + b As a result of studying the relation between the coefficients a, b and the physical properties of the gelatins, it was found that the coefficient a depended on the percentage of high molecular components in file gelatin. If uns clear that the viscosity of the modified gelatins irradiated with the ultrasonic wave influenced their gelling characteristics.

A flow-through electrolysis cell, named an electrochemical filter (ECF), with a three-electrode configuration was developed for the elimination and determination of electrochemically active components in biofluids, which give generally a nonspecific response to electrochemical biosensors. The use of a reference electrode ensured the precise control of the working electrode potential of the ECF and thus the quantitative current efficiency of the electrolysis. A flow-injection analysis setup was constructed by connecting two ECFs and a flow-through amperometric biosensor for glucose in series for the direct and simultaneous determination of glucose and uric acid in serum. The first ECF coulometrically determined uric acid, and the second one eliminated interferents with the biosensor: the sample was thus treated on-the-fly and then delivered to the biosensor, so that it determined glucose amperometrically without interference. The concentrations of glucose and uric acid measured in human control sera agreed well with the values determined with conventional methods. The system exhibited the wide dynamic range in the high glucose concentration region, thus can be applied to the analysis of serum of hyperglycaemic patients.

N'-acyl-phenylhydrazines (R-Ph-NHNH-COR') were oxidized in H2O/CH3CN (1:1) solution pH 11.5 by electrolysis or by the reaction with p-benzoquinone (Q) and the following reactions were investigated using electrochemical methods. The cathodic wave attributed to N'acyl-N-phenyldiazenes (R-Ph-N = N-COR') was rapidly replaced by a more negative cathodic wave (half-wave potential approximate to 0.7 V vs. SCE). No other anodic wave was observed, except that of the oxidation of R-Ph-NHNH-COR'. N-Phenyldiazenes (R-Ph-N = NH) might be attacked by Q and R-Ph-N = N-COR' and the cathodic wave observed at -0.7 V might be attributed to the reduction of the oxidized form of R-Ph-N = NH. The redox potential of R-Ph-N = NH is negative enough to inject electrons directly into the conduction band of silver halides.

It has been known that the setting time of gelatin solution may be measured readily by the thermal sensor method. The relation between the setting time (t), the solution concentration (C) and the cooling temperature (T) could be represented empirically as lnt = a . (C/T) + b. (a,b : the coefficients). In the present paper, the relation of these three factors is re-examined and the following empirical formula proposed. t = a . (C/T)(-1) + b. This equation is applied to two types of the 4th IAG gelatins (M-8929, PB-1185) to find their gelling characteristics and the correlation between the t-value and the C/T value. This empirical formula could consequently be employed in the study of these relationships for gelatin solution concentrations in the range 4 % to 10 %.

We have studied the effect of the thermal history on the gelation of an aqueous solution of gelatin by differential scanning calorimetry (DSC). DSC has shown that the heat of fusion and the melting point of gelatin gels are related to the maturing temperature. An experimental study of the structure of gelatin gels by wide angle X-ray diffraction (WAXD) is described. Some workers have reported that the presence of a crystalline structure was not seen in the WAXD pattern of gelatin gels containing a high amount of water, therefore, we made gelatin gels at several fixed temperatures and dried them at the same temperatures. The gelatin films made under such controlled temperature conditions were used as the samples for WAXD determination. The gelatin film gelled and dried at a higher temperature had a lower content Of triple-helices but denser bundles of the triple helices in the junction zone than the gelatin film made at a lower temperature. The heat of fusion and the melting point of gelatin gels obtained by DSC can be explained on the basis of the results concerning the structures of gelatin films obtained by WAXD.

It was attempted with an arylthio leaving pyrazolone magenta coupler to obtain rate constants for the two steps involved in the dye formation process, namely the formation of leuco dye and its conversion to dye, by monitoring the absorbance changes because of formation and disappearance of quinonediimines, quinonemonoimines, and dye during diffusion-limiting anodic oxidation of Kodak CD-1, using a spectroelectrochemical method. The rate constant for the formation of leuco dye was found to be larger than 10(5) M-1 sec-1, but a quantitative value could not be determined. Two different paths are suggested for conversion from leuco dye into dye, namely elimination (0.02 sec-1) and oxidation by quinonediimines (1.2 x 10(3) M-1 sec-1). The coupling rate was much greater than 1.8 x 10(3) M-1 sec-1 with the same type of four-equivalent coupler.

Carbon tissues prepared using types of gelatin differing in raw material and process were sensitized by dichromate and their photographic characteristics were investigated. Sensitivity and gamma were dominantly determined by the higher molecular weight components of the gelatin, sharpness and resolving power were dominantly determined by viscosity; these properties were little affected by its origin.

It is known that gel strength of gelatin is at first increased and then decreased by ultrasonic wave irradiation. In order to investigate the kinetics of this fact more minutely, fractionated gelatin was irradiated with ultrasonic waves and ultrasonic degradation constants for each fraction were calculated from the molecular weight distribution of the fractionated gelatins. It was found that the degradation process of the a component, as well as larger components of gelatin, was of the first order. The higher the molecular weight, the larger was the degradation constant.

Gelatins possessing widely different molecular weight distributions were prepared from a single gelatin by ultrasonic irradiation. Carbon tissues prepared using these gelatins were sensitized by dichromate, and their photographic characteristics were investigated. Sensitivity and gamma values increased with increasing higher molecular weight components, whereas the contrast transfer function and the acutance decreased with them. The hardened structure of the gelatin layer was also dependent on the molecular weight distribution. From the exposure dependence of the molecular weight distribution of the washed-off gelatin it was elucidated that the higher molecular weight components have the higher sensitivity.