ABSTRACT
Gamma irradiation of poly-L-serine was carried out in dilute aqueous solutions (50 micrograms/ml) in the dose range 0.44-2.64 megarad. Damage to the peptide bond studied through u.v. spectral absorption and gel filtration on a Sephadex G50 column and damage to the serine side groups through t.l.c. and amino acid analysis of the hydrolyzed samples indicate higher radiosensitivity of the side groups as compared to that of the peptide bond even in the megarad range. Early damage to the serine side groups seems to result in the formation of glycine.
Subject(s)
Peptides/radiation effects , Amino Acids/analysis , Autoanalysis , Chromatography, Gel , Chromatography, Thin Layer , Dose-Response Relationship, Radiation , Gamma Rays , Spectrophotometry, UltravioletSubject(s)
Dinitrofluorobenzene , Nitrobenzenes , Serum Albumin, Bovine , Animals , Cattle , Chemical Phenomena , Chemistry , Surface PropertiesABSTRACT
Studies of binding of ethidium bromide and quinacrine hydrochloride to native DNA at low ionic strength indicate that for both compounds the binding is selective, with about one binding site for about four nucleotides. Annealing of unfractionated histones to DNA by a salt-gradient dialysis method slightly decreases the binding of the dyes to DNA. Similar observations made with reconstituted preparations by using individual histone fractions reveal that the arginine-rich histones (histones H3 and H4) are most effective in decreasing the binding. The binding studies with ethidium bromide at high ionic strength and with denatured DNA show that strong dye binding to DNA is strongly dependent on the ionic strength and on the secondary structure of DNA. The histones are not effective in decreasing the dye binding under conditions of high ionic strength. The results are consistent with the observations [Oliver & Chalkley (1974) Biochemistry13, 5093-5098; Axel, Melchoir, Sollner-Web & Felsenfield (1974) Proc. Natl. Acad. Sci. U.S.A.71, 4101-4105] that histones form some kind of surface structures on DNA through non-specific interactions and [Kornberg & Thomas (1974) Science184, 865-868; Kornberg (1974) Science184, 868-871; D'Anna & Isenberg (1974) Biochemistry13, 4992-4997; Vandegrift, Serra, Marve & Wagner (1974) Biochemistry13, 5087-5092] that the tendency of arginine-rich histones to aggregate may be an important factor in determining the structure of chromatin.
Subject(s)
DNA/metabolism , Ethidium/metabolism , Histones/metabolism , Quinacrine/metabolism , Binding Sites , Nucleic Acid Denaturation , Osmolar Concentration , Protein BindingSubject(s)
Antibodies, Neoplasm , Antigens, Neoplasm , Sarcoma/immunology , Adolescent , Adult , Cell Line , Child , Female , Fluorescent Antibody Technique , Humans , Male , Middle Aged , Sarcoma/geneticsSubject(s)
Tendons/physiology , Animals , Biophysical Phenomena , Biophysics , Collagen/physiology , Contractile Proteins/physiology , In Vitro Techniques , Rats , TailABSTRACT
With a view to ascertaining the possible role of water content of the cells in the reported elevated values for proton spin-lattice relaxation time (T1) in malignant tissues, measurements of percent water content as well as T1 were undertaken in 68 cases of normal and concerous tissues from diverse sites in human patients. T1 values for the uninvolved samples were found to lie in the range of 400-1000 msec while the corresponding range for the involved samples was from 450-1520 msec. Water content of both normal and uninvolved tissues mostly lay in the narrow range of 70-90%. Occasionally samples with large T1 values showed lower water content as well. Data obtained weakens the case for characterization of tumor cells on the basis of their water content alone.
