Lower Denaturation Temperature Research Articles

Physicochemical and Functional Properties of Hen Ovalbumin Dephosphorylated by Acid Phosphatase

Hen egg ovalbumin is a mixture of three kinds of proteins, A1, A2, and A3 with two, one, and no phosphoryl residues, respectively. These three proteins were obtained by acid phosphatase treatment and then chromatography on a DEAE cellulofine AH column. The isoelectric points of A1, A2, and A3 were found by isoelectric focusing to be pH 4.75, 4.89, and 4.94, respectively. The denaturation temperature of each protein was examined by differential scanning calorimetry at its own isoelectric point and at pH 4.65. At both pHs, A3 had a lower denaturation temperature than A2 or A1. The surface tension of an A3 solution reached a constant more quickly than A1 or A2 after formation of a new surface of the solution. These results indicate that the completely dephosphorylated ovalbumin A3 is more susceptible to heat and surface denaturation than phosphorylated ovalbumin is. The difference in the heat aggregation patterns of A1, A2, and A3 solutions at different pH or salt concentrations showed that the electrostatic-repulsive force is important in helping to prevent the random aggregation of denatured ovalbumin.

Physicochemical and functional properties of hen ovalbumin dephosphorylated by acid phosphatase.

Hen egg ovalbumin i a mixture of three kinds of proteins, A1, A2, and A3 with two, one, and no phosphoryl residues, respectively. These three proteins were obtained by acid phosphatase treatment and then chromatography on a DEAE cellulofine AH column. The isoelectric points of A1 A2, and A3 were found by isoelectric focusing to be pH 4.75, 4.89, and 4.94, respectively. The denaturation temperature of each protein was examined by differential scanning calorimetry at its own isoelectric point and at pH 4.65. At both pHs, A3 had a lower denaturation temperature than A2 or A1. The surface tension of an A3 solution reached a constant more quickly than A1 or A2 after formation of a new surface of the solution. These results indicate that the completely dephosphorylated ovalbumin A3 is more susceptible to heat and surface denaturation than phosphorylated ovalbumin is. The difference in the heat aggregation patterns of A1, A2, and A3 solutions at different pH or salt concentrations showed that the electrostatic-repulsive force is important in helping to prevent the random aggregation of denatured ovalbumin.

Structure of a new pyrimidine from Bacillus subtilis phage SP-15 nucleic acid.

THE unusual modified base1 of the nucleic acid of the large, generalized transducing phage of Bacillus subtilis SP-15 was predicted from the low denaturation temperature of the native nucleic acid. The base was detected as a fifth ultraviolet-absorbing component once the nucleic acid had been hydrolysed with formic acid; it partially replaces the thymine and represents 12 mol per cent of all the bases1. It is responsible for the low Tm of the nucleic acid, since once all other unusual components have been removed, the remaining material melts at the same temperature as the native nucleic acid. We report here the isolation and characterization of this new pyrimidine.

The characterization of collagen from the swim bladder of the hake, Merluccius hubsii

The acid-extracted collagen of hake swim bladders prepared in highly purified form was characterized by its physicochemical properties and chemical composition. Chemical studies included quantitative amino acid analysis; hexose, aldehyde, and ester-like bond determinations and measurement of relative amounts of α, β, and γ components of the molecule. The unusually low denaturation temperature of 19 ° found for this collagen correlates well with its low content of proline and hydroxyproline, but apparently has no connection with the amount of hexoses, aldehyde groups, and ester-like bonds; furthermore, present data, together with that already existing in the literature, seem to indicate that the stability of the collagen molecule is not dependent on the proportion of β dimers and γ trimers.