333 research outputs found
Random Coil Behaviour of Proteins in Concentrated Urea Solutions
Measurements have been made of the intrinsic viscosities and
osmotic pressures of protein polypeptide chains in concentrated
urea solutions, in the presence of- ~-mercaptoethanol. The results
show that both properties depend on molecular weight exactly
as predicted for randomly coiled linear polymer chains. It can
therefore be assumed that protein polypeptide chains, in the
solvent medium employed, are random coils, r etaining practically
no elements of their native conformation. In addition, from the
osmotic pressure data, second virial coefficients have been calculated.
By combining the intr insic . viscosities and second viri.al
coefficients the unperturbed dimensions of protein polypeptide
chains have been obtained. Their values , are in good agreement
with those determined from the viscosity data alone
Random Coil Behaviour of Proteins in Concentrated Urea Solutions
Measurements have been made of the intrinsic viscosities and
osmotic pressures of protein polypeptide chains in concentrated
urea solutions, in the presence of- ~-mercaptoethanol. The results
show that both properties depend on molecular weight exactly
as predicted for randomly coiled linear polymer chains. It can
therefore be assumed that protein polypeptide chains, in the
solvent medium employed, are random coils, r etaining practically
no elements of their native conformation. In addition, from the
osmotic pressure data, second virial coefficients have been calculated.
By combining the intr insic . viscosities and second viri.al
coefficients the unperturbed dimensions of protein polypeptide
chains have been obtained. Their values , are in good agreement
with those determined from the viscosity data alone
Hydrogen Cyanide in the Rhizosphere: Not Suppressing Plant Pathogens, but Rather Regulating Availability of Phosphate
Enthalpy of Denaturation of Chymotrypsinogen A in Aqueous Urea Solutions
Urea has been known as a strong denaturant for globular proteins. Numerous papers have been published in which the denaturing action of urea is described and attempts have been made to explain this action. Appropriate models have also been developed in order to calculate or at least estimate the difference in free enthalpy (i: G) between the native and denatured forms of protein molecules in urea solutions. For a number of proteins, e.g., B-lactoglobulin, L G\u27s for urea denaturation at different temperatures have been obtained by optical methods, e. g. difference spectroscopy or optical rotatory dispersion, and from them van\u27t Hoff\u27s enthalpy. For a detailed survey, the reader is referred to the review article of Tanford
The Partial Specific Volume of P-Lactoglobulin A in Aqueous Urea Solutions
The partial specific volume of ~-lactoglobulin A in 0.02 M
NaCl - 0.01 M HCl containing different amounts of urea has
been determined from density measurements. The partial specific
volume first increases with urea concentration, reaches a maximum,
decreases, reaches a minimum, and then increases again.
In the interpretation of this behavior, the binding of urea to
the protein and the imperfect atomic packing in native protein
molecules have been assumed to be the dominant factors. From
dilatometric experiments the differences between the partial
molar volume of the protein in 0.02 M NaCl-0.01 M HCl with
and without urea have been obtained. The values of the differences
agree satisfactorily with those calculated from the partial
specific volume. Furthermore, the volumes as well as their changes
reflect the interaction of urea with the protein. Dilatometric
experiments were also performed with the protein in 0.02 M NaCl
to which urea was added. Comparison of the obtained results
with those in 0.02 M NaCl-0.01 M HCl displays the fact that
the partial specific volume is pH-dependent
The Activity Coefficients of Amino Acids and Peptides in Aqueous Solutions Containing Guanidinium Chloride
Six systems of the type amino acid- or peptide-guanidinium
chloride-water have been investigated over wide solute molality
ranges using vapor pressure osmometry. The amino acids used
were glycine and L-leucine, while the peptides were diglycine,
triglycine, glycyl-L-leucine and L-leucyl-L-leucine. Equations for
the ratios of the activity coefficients of these compounds in the
salt solutions and water, respectively, were obtained in terms of
the molalities of the solutes. The activity coefficient ratios for
glycine are not much below one, whereas those for i.-leucine are
considerably smaller reflecting the presence of the leucyl side
chain. The activity coefficient ratios for the peptides are generally
smaller than those for the amino acids which can be attributed to
. the presence of the peptide group
Pattern of Elemental Release During the Granite Dissolution Can Be Changed by Aerobic Heterotrophic Bacterial Strains Isolated from Damma Glacier (Central Alps) Deglaciated Granite Sand
Colonisation and weathering of freshly deglaciated granite are key processes in initial soil formation and development. We have obtained 438 isolates from granite sand covering glacial toe, 284 isolates at 22°C and 154 at 4°C incubation temperatures, respectively, to obtain cultures for the investigation of their weathering capabilities under laboratory conditions. The isolation of bacteria from granite sand was performed on rich-, intermediate- and low-nutrient-content solid media. Isolates were identified by 16S rRNA gene sequencing. According to the genera-associated weathering capabilities described in the literature and according to their abundance in our culture collection, we selected eight strains to analyse their effects on the weathering dynamics of granite sand during the batch culture experiment. Analysis of culturable bacteria showed higher species richness among isolates from 22°C than from 4°C incubations. In the R2A and 1/100 Ravan media, we observed the highest species richness of isolates obtained at 22°C and 4°C incubation temperatures, respectively. The obtained 16S rRNA sequences revealed the presence of alpha-, beta- and gamma-proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. The most numerous group of isolates was distantly related to Collimonas representatives, and according to the sequences of the 16S rRNA genes, they can form a new genus. Isolates from this group had the capability of causing increased dissolution rates for Fe, W, Ni and Rb. In general, at each sampling during the 30-day experiment, every strain showed a unique weathering profile resulting from differential rates of the dissolution and the precipitation of different minerals in the batch culture. Consequently, the presence of different strains, their growth stage and changes in proportions of strains in the bacterial community can affect further soil development and the successive colonisation by plant
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