Radiation Chemistry of Foods

When 10^?3m cysteine solution was irradiated in the presence of glucose at the concentration of ten-fold of cysteine, the G-values of products produced from cysteine were similar to those from 10^?3m cysteine solution. On the other hand, the yield of carbonyl compound from glucose was suppressed completely by interaction between cysteine and radicals which are secondarily produced from glucose.

Methionine could not suppress the yield of carbonyl compound from glucose, and, G-values of products from methionine varied in comparison with those from solution containing methionine only.

From the results using scavenger, it was concluded that oxidation to methionine sulfoxide and cleavage to α-aminobutyric acid was caused by OH and attack, respectively.     

Aromatic Amino Acid Residues in Japanese-radish Peroxidase a and Apoenzyme†

The nature of aromatic amino acid residues in Japanese-radish peroxidase a and the apoprotein was investigated by means of spectrophotometry and fluorospectrophotometry. The tyrosine residues in the holoenzyme were masked in the alkali-titration, giving an abnormally high value of 12.6, while they were exposed in the apoenzyme, exhibiting a value of 10.8. The difference spectra in the ultraviolet region between the holo-and apo-enzyme showed characteristic bands of tryptophan and phenylalanine as well as tyrosine. The perturbation of the aromatic amino acid residues by 50% ethyleneglycol was observed in the apoenzyme but not in the holoenzyme. The fluorophotometric experiments also revealed that the aromatic amino acid residues were in different environments in the holo- and apoenzyme. The difference between the conformation of peroxidase and that of the apoprotein was discussed.     

Substrate Specificity of α-Glucosidase II in Rice Seed

The substrate specificity of rice α-glucosidase II was studied. The enzyme was active especially on nigerose, phenyl-α-maltoside and maltooligosaccharides. The actions on isomaltose and phenyl-α-glucoside were weak, and on sucrose and methyl-α-glucoside, negligible. The α-glucans, such as soluble starch, amylopectin, β-limit dextrin, glycogen and amylose, were also hydrolyzed.

The ratio of the maximum velocities for hydrolyses of maltose (G₂), nigerose (N), kojibiose (K), isomaltose (I), phenyl-α-maltoside (?M) and soluble starch (SS) was estimated to be 100: 94.4: 14.2: 7.1: 89.5: 103.1 in this order, and that for hydrolyses of malto-triose (G₃), -tetraose (G₄), -pentaose (G₅), -hexaose (G₆), -heptaose (G₇), -octaose (G₈), and amyloses ( and ), 113: 113: 113: 106: 113: 100: 106: 106. The Km values for N, K, I, ?M and SS were 2.4 mm, 0.58 mm, 20 mm, 1.6 mm and 5.0 mg/ml, respectively; those for G₂, G₃, G₄, G₅, G₆, G₇, G₈, and , 2.4 mm, 2.2 mm, 2.1 mm, 1.5 mm, 1.0 mm, 1.1 mm, 0.95 mm, 1.5 mm and 1.1 mm.

Rice α-glucosidase II is considered an enzyme with a preferential activity on maltooligosaccharides.     

13C-NMR Spectra and Streochemistry of Isoechinulins A,B and C

¹³C-NMR spectra of isoechinulins A, B and C, metabolites from Aspergillus ruber, were fully assigned on the basis of chemical shifts and multiplicities and comparison with their analogues. Taking advantage of the symmetrical structure of the diketopiperazine ring, the stereochemistry of the trisubstituted carbon-carbon double bond in a dehydrotryptophyl moiety was determined as Z (cis) by measuring the coupling constants, , in the proton nondecoupled spectrum of isoechinulin B.     

Effects of pH,Ionic Strength,Temperature, and Complexing Anions on the Sorption Behavior of Cobalt on Hydrous Silica

Sorption of Co(II) on SiO₂.xH₂O (silica gel) has been investigated as a function of time, amount of silica gel (0.10–1.00g), cobalt concentration (5.00 × 10^?5–1.20 × 10^?3 M), ionic strength (0.20–1.40 M NaClO₄), pH (～6.80–10.80), and temperature (273–318 K). Using the sorption kinetics data, the diffusion coefficient of Co(II) was calculated to be 6.86(±0.44) × 10^?12 m²sec^?1 under particle diffusion-controlled conditions. The sorption rate was determined as 2.61(±0.19) × 10^?3 sec^?1 at 298 K, pH 6.70(±0.05) and 0.20 M NaClO₄. The sorption data followed the Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) isotherms. Cobalt sorption decreased with increased ionic strength. A gradual decrease in pH with increased ionic strength supported the sorption of Co(II) by an ion exchange mechanism. The effects of different ligands such as , F^?, and on the sorption of Co(II) were studied in the pH range 6.50 to 8.50. The sorption of cobalt on silica gel increased with increased temperature and had an endothermic enthalpy change (ΔH = 23.60(±0.57) kJ/mol).     

Photoperiodic control of tetrasporangium formation in the red alga Rhodochorton purpureum

Six geographical isolates of Rhodochorton purpureum (Lightfoot) Rosenvinge (Rhodophyta, Nemalionales) formed tetrasporangia only in short days at 10°C. For most isolates, the critical day-length increased with latitude of origin from 9.5 h for an isolate from California to 14.5 h for one from Antarctica. Tetrasporangium production could be induced by 9–15 short-day cycles followed by a further 22–28 cycles in long days. A night-break consisting of 1 h of white light in the middle of a 16-h dark period inhibited the short-day response of isolates from low latitudes, but not those from higher latitudes. When a similar night-break was given in the middle of a 14-h dark period, however, the response of all isolates was at least partially inhibited. Night-breaks given at any time in the central 7 h of a 14-h dark period were equally inhibitory. Broad-band red light (0.3–0.4 mmol m^-2), given as a night-break, caused 50% inhibition of the short-day response. At a slightly higher photon exposure (0.6 mmol m^-2, given as 1 μmol m^-2 s^-1 for 10 min), narrow-band red (662 nm) and blue (448 nm) light caused similar inhibition, but green (547 nm) and far-red (731 nm) were ineffective as night-breaks. The inhibitory effect of a 10-min night-break with red light could not be reversed by subsequent exposure to an equal photon exposure of far-red light. These results add to the existing evidence that the pigments mediating photoperiodic responses among algae are more varied than those among flowering plants.     

Isolation and Characterization of Globulin from Seeds of Amaranthus hypochondriacus L.

Seeds of grain amaranths contain a high amount (about 60% of total nitrogen) of albumin and globulin and a trace amount of prolamin. From salt-soluble extracts of A. hypochondriacus seeds, a globulin (440,000 in apparent molecular weight and ) was purified by Sepharose 6B gel and DEAE-cellulose column chromatographies. The protein comprised at least four kinds of subunits whose molecular weights were 36,000, 32,000, 20,000 and 18,000, respectively. The amino acid composition of the globulin was almost similar to those of soybean and oat globulins.     

Pollen in packrat middens

Fossil packrat middens are used to reconstruct late Quaternary environments in the arid Western U.S.A. Airborne pollen is contributed to middens both directly from the air, and through adherence to plant macrofossils. I examined the filtration of atmospheric pollen by Larrea tridentata leaves (resinous, with sparse recumbent hairs), Cercidium microphyllum twigs (glabrous with recumbent hairs) and Sphaeralcea ambigua leaves (covered with stellate hairs) and evaluated the potential biases of scavenged pollen on the interpretation of pollen records from middens. Pollen grains collected from the surfaces of the plants were most numerous during the spring when (airborne) pollen concentrations were high. Of the species investigated, the Sphaeralcea leaves filtered the greatest number of spring pollen grains from the air (3419 grains cm^?2); captured pollen was very low during other seasons. Sticky Larrea leaves continuously captured airborne pollen ( = 246 grains cm^?2). Pollen captured by smooth Cercidium was consistently low ( = 31 grains cm^?2). Only the spring pollen was filtered in sufficient numbers to obtain minimum pollen counts of 200 grains by all 3 taxa. The plants frequently captured greater proportions of their own pollen. Pollen content of packrat middens will reflect the season of plant macrofossil collection and the species composition of the plants incorporated.     

Guanosine Diphosphate Mannose in Conformational Relation to Other Suger Nucleotides and Phosphates in Solution

Molecular conformational transition of GDPMan and solution conformation of α-d- mannopyranose moiety in Man-l-P and GDPMan were examined in relation to other sugar nucleotides and phosphates. GDPMan and other sugar nucleotides examined revealed changes in the optical rotation in sigmoidal curve in water by addition of urea. The change was reversible without significant decomposition and is attributable to dissociation of an ordered form into a random form. Optical conformational values in 8m urea solution were+116° for GDPMan, +58°~+79° for UDPGlc, +79° for UDPGal, +135°~+143° for UDPGlcNAc, and +138°~ +155° for UDPGIcA.

NMR analysis and periodate oxidation study revealed the ⁴C₁ conformation of α-d-hexopyranose moieties in Man-1-P, Glc-l-P, GDPMan, UDPGlcNAc and UDPGalNAc.     

Two Forms of Glucoamylase from Mucor rouxianus 1. Purification and Crystallization

Mucor rouxianus produced two forms (isoenzymes) of glucoamylase which could be separated from each other by polyacrylamide gel electrophoresis or by chromatography on SP-Sephadex C-50, and they were designated glucoamylase I and glucoamylase II. Glucoamylases I and II were isolated in crystalline form, and were homogeneous in poly acrylamide gel electrophoresis and in ultracentrifugation, respectively. The sedimentation coefficient () molecular weight of glucoamylase I were 4.39 S and 59,000, and those of glucoamylase II were 4.29 S and 49,000, respectively.     

Studies on Oxidation-Reduction Potentials (ORP) of Microbial Cultures

At maximum production of l-glutamic acid, the oxidation-reduction potential of the culture broth in l-glutamic acid fermentation showed a stable value of 9.0 to 9.6 as rH value. When biotin concentration in the medium was high (40γ/liter), the production of l-glutamic acid decreased, and the rH was 8.0 and it was out of accordance with that of the control (biotin-poor; 2γ/liter). Under “less-aerobic” conditions, its rH rose to 10.4.

From these results, it was concluded that the rH during maximum production of l-glutamic acid showed a stable value affected actively by the redox system, l-glutamic acid/α-ketoglutaric acid and      

Effects of compound eye-removal on the photoperiodic response of the band-legged ground cricket, Pteronemobius nigrofasciatus

The band-legged ground cricket Pteronemobius nigrofasciatus shows a clear photoperiodic response at 25°C with respect to the control of the induction of embryonic diapause. When crickets were reared under a short-day (LD 12 12) photoperiod and then transferred to a long-day (LD 16 8) photoperiod upon adult emergence, the adults mainly laid nondiapause eggs. However, adults maintained continuously under short-day conditions laid dispause eggs. When compound eyes were bilaterally removed after adult emergence, the crickets mainly laid nondiapause eggs, irrespective of the photoperiod. Thus, the adults completely lost their sensitivity to photoperiod after bilateral removal of their compound eyes. Unilateral removal of the compound eye also affected the crickets under a short-day photoperiod, and the incidence of diapause eggs was intermediate between that laid by intact adults and that laid by adults after the bilateral removal of compound eyes. The incidence of diapause eggs in sham-operated crickets was not significantly different from that in intact crickets under both sets of photoperiodic conditions. These results show that P. nigrofasciatus perceives the photoperiod through its compound eyes.     

Differences in measurement of day-length and photoperiodism in two stocks from subarctic and temperate climates in the Carabid beetle Pterostichus nigrita F.

Summary Experiments on the measurement of day-length as a basis for photoperiodism were made with a stock of the carabid Pterostichus nigrita from the Subarctic in Swedish Lapland (64–66° N). Results were compared with those of earlier investigations on a Central European stock (51° N). P. nigrita from Lapland reacted differently from the Central European ones in experiments with abnormal photoperiods (cycle durations from 12 to 72 h; light period in all cases 8 h). Whereas, in the Central European stock, short-day induced reactions (previtellogenesis in the females, maturation of the male gonads) could only be observed if those cycles represented multiples of 24 h in whole numbers, short-day reactions in the Lapland stock were inducible with all cycles in nearly 100% of the specimens investigated (only in LD 8:4 was this percentage slightly diminished). Experiments with dark breaks of 2 h in extreme long-day (LD 20:4) revealed nearly 100% short-day maturation, irrespective of the temporal location of these dark breaks in beetles from the Lapland stock, whereas in Central European beetles only dark breaks during certain scotophile phases had such an effect. In the Central European P. nigrita, two hour light breaks during the night phase of an LD 14:10 had a destructive effect on short-day maturation processes; in the Lapland stock, these were possible in spite of 1 h light breaks during the night of an LD 19:5. In the Lapland stock, developmental processes which in the Central European stock are confined to short-day conditions could occur in all types of experiments, provided that about 3 to 4 h of darkness were given during each 24 h cycle, whether uninterrupted or not.Light break experiments revealed that the long-day process for ovarian development (vitellogenesis) is induced in the same way as with the Central European P. nigrita. It occurs if light falls into a photosensitive phase during the second half of the 24 h cycle.Thus, for the Subarctic population, a model is proposed in which short-day is measured by means of an hour-glass timer, whereas long-day is perceived by means of a circadian oscillator.Supported by Deutsche Forschungsgemeinschaft (Schwerpunktporgramm: Biologie der Zeitmessung)     

Photoperiodic induction of the first and the second diapause in the bean bug,Riptortus clavatus: a photoperiodic history effect

Summary In nondiapause adults raised under a long-day photoperiod, the critical daylength for diapause induction was between 13 and 14 h although some individuals did not respond to the short-day photoperiod and went on laying eggs. In postdiapause adults in which LD 1311 induced the first diapause (L13 insects), the critical daylength for diapause reinduction was between 13 and 14 h, whereas it was between 12 and 13 h in postdiapause adults in which LD 1014 induced the first diapause (L10 insects). Under LD 1311, a small proportion of L10 insects went into the second diapause after great delay as compared with L13 insects. Under LD 1014, on the other hand, L10 insects went into the second diapause more rapidly than L13 insects. Therefore, the photoperiod which had induced the first diapause affected the photoperiodic induction of the second diapause not only in the critical daylength but also in the speed of response. In Riptortus clavatus, the photoperiodic history influences the subsequent photoperiodic response even after a physiological state induced by the previous photoperiod was terminated completely.Abbreviations L13 insects postdiapause adults in which LD 1311 induced the first diapause - L10 insects postdiapause adults in which LD 1014 induced the first diapause