Fast atom bombardment: A new mass spectrometric method for peptide sequence analysis

We have studied a selection of peptides using a new mass spectrometric ionisation technique - fast atom bombardment (FAB). We define the fragmentation pathways observed and comment on the utility in sequence analysis. A simple acetylation experiment is shown to aid rapid sequence assignment.     

Vascular smooth muscle mitochondria: Magnesium content and transport

Endogenous magnesium content and magnesium transport of isolated bovine vascular smooth muscle mitochondria were studied. Mitochondria isolated from atherosclerotic bovine arteries contained two to three times as much magnesium (178 nmol/mg of mitochondrial protein) as those isolated from normal arteries (67 nmol/mg of mitochondrial protein). Electron-opaque granules were visible in the unstained unfixed mitochondria and could be shown with electron probe analysis to consist of magnesium, calcium, and phosphorus. At concentrations of external Mg²⁺ from 0 to 6 mm, the vascular smooth muscle mitochondria exhibited respiratory substrate-supported release of Mg²⁺ as studied with metallochromic indicator, eriochrome blue, using dual-wavelength spectrophotometry. The maximal velocity of energized release (3 nmol of Mg²⁺/s/mg of mitochondrial protein) was observed at 4 mm external Mg²⁺ and the half-maximal transport occurred at 0.5 mm.     

The amino acid sequence of chick skin collagen α1-CB7: The presence of a previously unrecognized triplet

Because alignment of the amino acid sequences of chick skin collagen α2-CB3 (1) with the relevant portion of chick skin collagen α1-CB7 (2) suggested that a Gly-X-Y triplet may have been missed in the latter, the peptide TM-2, produced by tryptic digestion of maleylated α1-CB7, was reinvestigated. Cleavage by trypsin at the unblocked lysine at position 18, and isolation of the resulting COOH-terminal peptide, showed this to be a 15-residue peptide containing a previously unrecognized Gly-Pro-Hyp triplet. Sequencing of the peptide showed this to occupy positions 4 through 6, or 56 through 58 of α1-CB7. The latter thus has 271 instead of 268 residues, and the α1[I] chain 1055 instead of 1052.     

Isolation and properties of a ferredoxin from Anabaena Flos-Aquae

Ferredoxin was isolated from the blue-green alga Anabaena flos-aquae. Its homogeneity was shown by conventional and SDS-polyacrylamide gel electrophoresis, and isoelectric focusing on polyacrylamide gel columns, the latter indicating a pI at ca pH 3·7. The absorption spectrum had, in the oxidized state, maxima at 462, 421, 327 and 276 nm, with a shoulder at 284 nm, a spectrum characteristic of plant-type ferredoxins. The 421 : 276 nm absorbance ratio was typically 0.49. The ferredoxin effectively mediated the photoreduction of NADP⁺ by barley chloroplasts depleted of native ferredoxin. The MW obtained by sedimentation-equilibrium and sedimentation velocity-diffusion coefficient studies was ca 12 000 daltons, a value somewhat higher than suggested by amino acid composition data. The ferredoxin contained 2Fe and 2S per molecule.     

A cutin acid in Pinus sylvestris microspores

Nonacosan-10-ol (0.7%) and the cutin acid, 9,16-dihydroxyhexadecanoic acid (0.3%) are present in Pinus sylvestris microspores. The pollen coat hence has some features in common with leaf cuticles.     

Reconstitution of pig lymphocyte plasma membranes from solubilized components, with particular reference to membrane-associated immunoglobulins

Plasma membranes of lymphocytes obtained from pig mesenteric lymph nodes were reconstituted after solubilization with bile salts. The proportion by weight of immunoglobulin in the reconstituted membrane was no greater than about 5-10% of that in the original membrane. Possible reasons for the low reincorporation of immunoglobulin are discussed.