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P Johnson

Publications and source records attributed to P Johnson.

At least 649 records · Page 36Linked to original sources
PubMed1970

Biological activity and the 3-methylhistidine content of actin and myosin.

1. The 3-methylhistidine content of myosin varies according to muscle type. It is highest in myosin from white skeletal muscle and lower values are obtained from myosin of red skeletal and smooth muscle. 2. The 3-methylhistidine content of actin was similar in all of the types of muscle from which it was isolated. 3. The 3-methylhistidine of rabbit actin is localized in a single tryptic peptide that was readily modified during fractionation procedures. 4. Photo-oxidation studies indicated that the 3-methylhistidine residues are not essential for adeonsine triphosphatase and actin-combining activities of myosin. 5. During photooxidation G-actin lost completely the ability to polymerize to the F form before all the 3-methylhistidine was destroyed.

Adenosine Triphosphatases↗
PubMed1969

The importance of life-time changes in fluorescence depolarization.

The rotational relaxation time, rho, calculated from measurements of fluorescence depolarization, is clearly dependent on the assumed mean life-time, tau, of the excited state. However, variations in tau with experimental conditions (temperature and solvent composition) occur and the effect of such alterations in tau is demonstrated. In particular it should be noted that, unless life-time changes can be excluded, the occurrence of linear plots of reciprocal degree of polarization against the temperature/viscosity ratio does not necessarily indicate the absence of intramolecular freedoms. An attempt to correct for such life-time changes by measurement of the fluorescence intensity is made for the bovine serum albumin-1-dimethyl-aminonaphthalene-5-sulphonyl chloride system. The value of rho/3tau thus obtained for this system at 20 degrees is approx. 4.7, as against approx. 3.4 obtained by several workers in the absence of life-time corrections.

Amines↗
PubMed1968

Chemical studies on the cysteine and terminal peptides in tryptic digests of actin.

1. On exhaustive digestion of carboxymethylated actin in 6m-urea solutions with carboxypeptidase A, 1 mole of phenylalanine was liberated/43000g. of protein. At a lower urea concentration and in the absence of urea, carboxymethyl-cysteine (CMCys) was also liberated. 2. Three cysteine-containing peptides were identified by the study of peptide ;maps' of tryptic digests of actin treated with thiol reagents. 3. The three peptides, each containing one residue of CMCys, were isolated from tryptic digests of carboxymethylated actin by ion-exchange chromatography. 4. One of these peptides was possibly the N-terminal peptide and contained about 17-18 residues; another was CMCys-Asp-Ile-Asp-Ile-Arg; the other, CMCys-Phe, was the C-terminal tryptic peptide. 5. The chemical evidence suggests that the actin molecule consists of a single polypeptide chain of molecular weight about 44000.

Amino Acid Sequence↗