Thermal Properties of Freeze-Concentrated Sugar-Phosphate Solutions

In order to understand the effect of phosphate salts on the freeze-concentrated glass-like transition temperature (T _g′) of aqueous sugar solutions, two types of sugar (glucose and maltose) and five types of phosphate salts (Na₃PO₄, Na₄P₂O₇, Na₅P₃O₁₀, K₃PO₄, and K₄P₂O₇) were employed, and the thermal properties of various sugar-phosphate aqueous systems were investigated using differential scanning calorimetry. The T _g′ of glucose increased with increasing sodium phosphates up to a certain phosphate ratio, decreasing thereafter. The maximum T _g′ value was slightly higher in the order of Na₃PO₄ > Na₄P₂O₇ ≥ Na₅P₃O₁₀. Maltose-sodium phosphate also showed a similar trend as glucose-sodium phosphate samples. However, the degree of T _g′-rise of maltose systems was much less than that of glucose. It is thought that the T _g′ elevated by the molecular interaction between sugar and phosphate ions will be reduced by hydrated sodium ions. In comparisons between potassium phosphate and sodium phosphate, it was found that sugar-potassium phosphates showed the lower maximum T _g′ at a lower phosphate ratio than sugar-sodium phosphates. In addition, the T _g′ of potassium phosphates dropped sharply in comparison with sodium phosphates at the high phosphate ratio. These results suggest that potassium phosphates are lower T _g′ than sodium phosphates, and that potassium ion plays a better plasticizer than sodium ion. A certain amount of sodium phosphates (Na₃PO₄ and Na₄P₂O₇) caused devitrification. Potassium phosphates, however, did not show devitrification which can be explained by the fact that potassium ion can be dynamically restricted by sugar.     

Properties of Hemoglobin Solutions in Red Cells

The present studies are concerned with a detailed examination of the apparent anomalous osmotic behavior of human red cells. Red cell water has been shown to behave simultaneously as solvent water for nonelectrolytes and nonsolvent water, in part, for electrolytes. The nonsolvent properties are based upon assumptions inherent in the conventional van't Hoff equation. However, calculations according to the van't Hoff equation give osmotic volumes considerably in excess of total cell water when the pH is lowered beyond the isoelectric point for hemoglobin; hence the van't Hoff equation is inapplicable for the measurement of the solvent properties of the red cell. Furthermore, in vitro measurements of osmotic and other properties of 3.7 millimolal solutions of hemoglobin have failed to reveal the presence of any salt exclusion. A new hypothesis has been developed from thermodynamic principles alone, which predicts that, at constant pH, the net charge on the hemoglobin molecule decreases with increased hemoglobin concentration. The existence of such cooperative interaction may be inferred from the effect of pH on the changes in hemoglobin net charge as the spacing between the molecules decreases. The resultant movement of counterions across the cell membrane causes the apparent anomalous osmotic behavior. Quantitative agreement has been found between the anion shift predicted by the equation and that observed in response to osmotic gradients. The proposed mechanism appears to be operative in a variety of tissues and could provide an electrical transducer for osmotic signals.     

Propylene Oxide as Sterilizing Agent

Liquid propylene oxide added to a variety of disinfectant solutions resulted in a significant reduction of the bacterial spore content of these solutions.     

Sterilizing effects of trimethylphosphate in Drosophila melanogaster

Trimethylphosphate (TMP) causes aspermia in D. melanogaster males. If larvae are allowed to develop on standard maize-meal medium containing 0.002 M TMP or greater, the enclosing adult males, when placed on uncontaminated medium, exhibit a period of temporary sterility. Between test groups the period of sterility is most variable at the doses of 0.002-0.004 M, but at 0.005 M or greater is approximately 11-12 days. Near-lethal doses of about 20 g/kg by abdominal injection produces a temporary sterility in adults, whereas oral doses up to 0.02 M are ineffective. Oogenesis in females is not affected by doses which cause temporary sterility in males. In adult male D. melanogaster, which were treated as larvae with 0.01 M TMP in the food medium, the basal region of testes and seminal vesicles do not contain spermatozoa. Cytological examinations of the spermatids reveal ultrastructural changes which are characteristic of those seen in X/O and sterile-mutant males; they contain incomplete axial fibre complexes, abnormal development of the mitochondrial derivatives, and nuclei which fail to elongate and condense. Evidence from cytological studies of larval testes suggests that the chemosterilizing effect of TMP is upon early primary spermatocytes. This is also supported by mating data.     

Conformational Properties of Polyglutamine Sequences in Guanidine Hydrochloride Solutions

Two sets of iso-1-cytochrome c variants have been prepared with N-terminal insertions of pure polyglutamine, i.e., PolyQ variants, or polyglutamine interrupted with lysine every sixth residue, i.e., Gln-rich variants. The polymer properties of these pure polyGln or Gln-rich sequences have been evaluated using equilibrium and kinetic His-heme loop formation methods for loop sizes ranging from 22 to 46 in 1.5, 3.0, and 6.0 M guanidine hydrochloride (GdnHCl). In 6.0 M GdnHCl, the scaling exponent, ν₃, for the pure polyGln sequences, is ∼1.7—significantly less than ν₃ ≈ 2.15 for the Gln-rich sequences. The stability of the His-heme loops becomes progressively greater for the pure polyGln sequences relative to the Gln-rich sequences as GdnHCl concentration decreases from 6.0 to 1.5 M. Thus, the context of the sequence effects the polymer properties of Gln repeats even in denaturing concentrations of GdnHCl. Comparison of data for the Gln-rich variants with previous results for Gly-rich and Ala-rich variants shows that ν₃ ∼ 2.2 for the Gln-rich, Gly-rich, and Ala-rich sequences in 6.0 M GdnHCl, whereas ν₃ remains unchanged at 3.0 M GdnHCl concentration for the Gln-rich and Ala-rich sequences but decreases to ∼1.7 for the Gly-rich sequences. Thus, the polymer properties of Gln-rich and Ala-rich sequences are less sensitive to solvent quality in denaturing solutions of GdnHCl than Gly-rich sequences. Evaluation of Flory’s characteristic ratio, C_n, for the Gln-rich and Ala-rich sequences relative to the Gly-rich sequences shows that Gln-rich sequences are stiffer than Ala-rich sequences at both 3.0 and 6.0 M GdnHCl.     

一种大豆成熟种子的消毒方法

文中介绍的氯气消毒法可大大提高大豆成熟种子的消毒效率,且较其他几种方法萌发快,萌发率高。     

Impact of Phenolic Antioxidants on Structural Properties of Micellar Solutions

Antioxidants solubilized in micellar solutions can change micellar properties like the size and shape of micelles, critical micellar concentration (cmc) and viscosity. Interactions arising between antioxidants and the surfactant determine the locations of antioxidants and vice versa. The location and interaction are dependent on the type of both the antioxidant and surfactant. Influences of various antioxidants on the physical and structural properties were tested in micellar systems of cationic CTAB, non-ionic Brij 58 and anionic SDS. The antioxidants used to investigate the effects of gradually increasing lipophilicity were gallic acid (GA) and the gallate esters from methyl to octyl gallate (MG-OG). Hydroxy cinnamic acids (HCAs) like -coumaric acid (pC), caffeic acid (CA), ferulic acid (FA) and sinapic acid (SA) were employed to observe effects of functional groups like hydroxyl and methoxy groups. Micellar size and shape determined by small angle neutron scattering (SANS), viscosity and cmc were chosen to characterize the antioxidant influence. In Brij 58 systems propyl gallate (PG) did not affect the cmc or aggregation number but decreased micellar size slightly due to an intercalation of PG into the region of the polyoxyethylene chain and the first adjacent alkyl chain methylene groups. In SDS systems the micellar size and cmc decreased in the presence of PG. This was attributed to PG residing in the Stern layer. However, in CTAB systems micelles swelled at low PG concentration and in the presence of GA, while higher PG concentrations and more lipophilic antioxidants led to a sphere-to-rod transition with a simultaneous increase in viscosity and decrease in cmc. This revealed the intercalation of antioxidants in the palisade layer of CTAB micelles entering into strong interactions of electrostatic and hydrophobic origin. It could be demonstrated that the interactions became stronger the more lipophil an antioxidant is and the more hydroxyl groups are attached to the aromatic ring. Differences in the location and interaction of antioxidant and micelles are proposed as being responsible for the effectiveness of antioxidants.     

常压低温等离子体对微生物的杀灭研究

初步探讨APPJ等离子体对微生物的影响机制 ,用APPJ与DBD两种不同类型等离子体对不同代表微生物金黄色葡萄球菌、大肠杆菌、枯草杆菌黑色变种进行处理 ,分析比较不同微生物对不同等离子体的存活曲线 ;进而利用扫描电镜观察微生物细胞壁、膜等外部结构的变化。结果显示两种等离子体对不同微生物的杀灭作用均为先快后慢 ,APPJ的作用效果远好于DBD(DBD对金黄色葡萄球菌及枯草杆菌黑色变种芽孢的D值为 70s ,而APPJ的D值为 4s)。同时 ,在APPJ的作用下 ,大肠杆菌细胞壁、膜有明显破裂发生。这证明 ,APPJ可快速有效地杀灭微生物体 ,其灭菌机制可能与微生物细胞壁、膜的破裂有关。     

Peracetic Acid as Sterilizing Agent for Culture Serum

Serum, used to supplement cell culture media, is usually sterilized by filtration because heat-treatment may adversely affect its growth-promoting properties. This filter-sterilization procedure is, however, unreliable because viruses and mycoplasmas may easily pass through the filter. As another approach, we have studied the question of whether serum sterilized by peracetic acid can be used in cell and tissue cultivation. Preliminary results^1,2 indicated that this was possible and we have attempted to establish the best method of peracetic acid treatment and to show that serum treated in this way is suitable for cell cultivation.     

白芨多糖胶-瓜尔胶复配溶液的流变性

考察了瓜尔胶溶液和白芨多糖胶-瓜尔胶复配溶液的流变特性。两组溶液呈现典型的假塑性,不同浓度下两组溶液表观黏度(ηa)随剪切速率(τ)的变化可以用Ostwald-Dewaele方程描述。白芨多糖胶和瓜尔胶复配产生协同增效作用,复配溶液的ηa大于单一组分的白芨多糖胶溶液或瓜尔胶溶液的ηa。复配溶液中白芨多糖胶与瓜尔胶的最佳配比是质量比为9∶1。     

Sterilizing Effects of High-Intensity Airborne Sonic and Ultrasonic Waves

The lethal effects of high-intensity airborne sonic (9.9 kc/sec) and ultrasonic waves (30.4 kc/sec) on spores of Bacillus subtilis var. niger ATCC 9372 were determined. The spores, which were deposited on filter-paper strips, were exposed to sound waves for periods varying from 1 to 8 hr, at a temperature of 40 C and a relative humidity of 40%. Significant reductions in the viable counts of spores exposed to airborne sonic or ultrasonic irradiations were obtained. The antibacterial activity of airborne sound waves varied with the sound intensity level, the period of irradiation, and the distance of the sample from the sound source. At similar intensity levels, the amplitude of motion of the sound waves appeared to be a factor in acoustic sterilization.     

Sterilizing Bacillus pumilus spores using supercritical carbon dioxide

Supercritical carbon dioxide (SC CO(2)) has been evaluated as a new sterilization technology. Results are presented on killing of B. pumilus spores using SC CO(2) containing trace levels of additives. Complete killing was achieved with 200 part per million (ppm) hydrogen peroxide in SC CO(2) at 60 degrees C, 27.5 MPa. Addition of water to SC CO(2) resulted in greater than three-log killing, but this is insufficient to claim sterilization. Neither ethanol nor isopropanol when added to SC CO(2) affected killing.