Decreased Heat Stability Research Articles

Three glucose 6-phosphate dehydrogenase variants found in Japan.

Three Japanese glucose 6-phosphate dehydrogenase (G6PD) variants were investigated. G6PD 'Mediterranean-like' had markedly decreased activity, normal electrophoretic mobility, low Km G6P, low Km NADP, increased utilization of all three substrate analogues (2-deoxy-G6P, Gal-6P, and deamino-NADP) and slightly decreased heat stability and slightly biphasic pH curve. G6PD 'Ogori' had markedly decreased activity, but otherwise normal characteristics. G6PD 'Hofu' had moderately decreased activity, normal electrophoretic mobility, slightly reduced Km G6P, normal Km NADP, normal utilization of 2-deoxy-G6P and Gal-6P, but increased utilization of deamino-NADP and normal heat stability as well as normal pH curve.

An abnormal form of purine nucleoside phosphorylase in a family with a child with severe defective T-cell-and normal B-cell immunity

1. 1. Purine nucleoside phosphorylase and adenosine deaminase (ADA) were studied in normal red blood cells and lymphocytes and in the cells of a family with a child with a defective T-cell- and normal B-cell immunity. 2. 2. In the propositus no purine nucleoside phosphorylase (NP) activity could be detected in her red cells and lymphocytes, while the ADA activity was somewhat increased. The NP activities of the father, mother and brother of the propositus are in the heterozygote range. The decreased activity of NP was not only found for the substrate inosine but also when guanosine or xanthosine were used as substrate. The mode of inheritance is autosomal recessive. 3. 3. With starch gel electrophoresis no NP activity could be detected in the patient's haemolysate. The electrophoretic patterns of NP from the father, mother and brother of the patient seem to be the same as for normal NP with six bands of NP activity. 4. 4. The nucleoside phosphorylases of the father, mother and brother of the patient were characterized by an increased K M for the substrate inosine, normal pH optimum and a decreased heat stability.

Glucose phosphate isomerase deficiency with hereditary hemolytic anemia in a Spanish family: Clinical and familial studies

A new case of glucose phosphate isomerase deficiency associated with cogenital nonspherocytic hemolytic anemia is described in a 12-year-old girl of Spanish origin. The parents exhibited erythrocyte glucose phosphate isomerase activity between 50 and 60% of normal. The enzyme of the propositus had normal Michaelis-Menten constants both for F-6-P and G-6-P, but abnormal pH optimum and decreased heat stability at 48 degrees C. On starch-gel electrophoresis the father's enzyme was normal but the mother's showed a cathodic migrating band in addition to the normal one. The enzyme from the propositus exhibited only one band with cathodal mobility of 116% of the main band found in normal subjects. It is postulated that the propositus is double heterozygous for two abnormal alleles, and the mother contributes a mutant allele with abnormal electrophoretic mobility and thermolability at 48 degrees C whereas the father contributes an allele without enzymatic activity.

Activation of deoxyribonucleoprotein in human leucocytes stimulated by phytohemagglutinin: II. Structural changes of deoxyribonucleoprotein and synthesis of RNA

The increase in acridine orange (AO) binding sites in the DNP complex occurring in human leucocytes during the first 60 min after PHA stimulation was found to be paralleled by a decreased heat stability as well as a more regular arrangement and stretching of the DNP complex. These findings support the theory that the binding between DNA and surrounding proteins in the DNP complex is altered by the action of PHA and that thereby increasing numbers of DNA phosphate groups become uncovered. Increasing amounts of low ordered ribonucleic acids were found in mononuclear leucocytes if more than half of all AO binding sites became accessible to AO. Above this value a correlation was found between the number of AO binding sites in DNP uncovered during the initial phase of PHA stimulation, and the amount of low ordered RNA found 1 and 48 h after PHA administration. The data suggest that this activation of the DNP complex acts as one necessary trigger for RNA synthesis and that the role of basic proteins in gene regulation might be confined to this trigger process preceding a more specific and refined mechanism for gene regulation.

Preparation and thermal stability of organometallosiloxanes and organometallic compounds

AbstractThis study covers the results of synthesis and investigation of thermal stabilities of several organometallosiloxanes and organometal compounds containing Group IV elements. Investigations indicate, in general, that heat resistance is related to the dissociation energies of the MO bonds, the number of organic groups connected to the metal atom, and the structure of the molecule as a whole. More specifically, the substitution of GeO and SnO bonds for some SiO linkages in organosiloxanes produces a reduction in heat stability. The influence of the GeO bond to decrease the resistance of siloxanes is less than that of the SnO linkage; an increase in the number of SnO linkages producing a corresponding decrease in heat stability of the organosiloxane. The resistances of the germoxysiloxanes to heat degradation are less than that which would be expected from indications given by the relative stabilities of more simple organometallic compounds.

EVOLUTION OF A CATABOLIC PATHWAY IN BACTERIA.

Genetic derepression of ribitol dehydrogenase in a mutant of Aerobacter aerogenes, strain 1033, enabled it to grow on xylitol, a substrate of the enzyme, but not its inducer. A derivative strain with an improved rate of growth on xylitol was obtained from the first mutant. The faster growth rate was made possible by the production of an altered ribitol dehydrogenase, as demonstrated by an increase in its activity on xylitol relative to ribitol and by its decreased heat stability.

The Heat Stability and Feathering of Sweet Cream, as Affected by Different Homogenization Pressures and Different Temperatures of Forewarming

Summary 1. The heat stability of cream, measured in terms of time of coagulation at 120°C. as affected by butterfat content, temperature of heating before homogenization, and homogenization pressure has been determined. A definite relationship was found in their influence on heat stability. 2. An increase of homogenization pressure lowered the time of coagulation. Maximum stability resulting from preheating occurred when 80°C. was used, and minimum stability during sterilization occurred when 60°C. was used. An increase in butterfat content invariably lowered the heat stability of homogenized cream. 3. The same general relationship exists in pasteurized as in preheated cream, with the exception that the point of maximum heat stability shifts from 80°C. in preheated creams to approximately 70° to 74°C. in pasteurized creams. 4. Where pasteurization was practiced prevention of feathering was partially successful by the treatment producing maximum heat stability, namely pasteurization for thirty minutes at 70° to 74°C. 5. The basic criterion for predicting whether or not a cream will feather is quality. Acidity and H-ion concentration were used for quality determinations. Pure, fresh cream of 20 per cent butterfat content and of 0.15 per cent acidity can generally be pasteurized from 65° to 85°C. and homogenized at any pressure up to 3000 pounds without danger of feathering. With optimum treatment 0.165 per cent acidity is the danger line for feathering. 6. An increase of viscosity of preheated homogenized cream is accompanied by a decrease in heat stability. It is suggested that variation of potential upon the fat globules may be an important factor in determining the heat stability of the product. 7. In the preparation of sterile cream for market purposes maximum stability during sterilization was obtained by preheating to approximately 80°C. before homogenization.