N-terminal groups of buffalo thyroglobulin

N-Terminal analysis of purified buffalo thyroglobulin by the fluorodinitrobenzene method of Sanger yielded about 1.5 moles of DNP-glutamic acid per mole of buffalo thyroglobulin. No water-soluble DNP-amino acid was detectable as N-terminal. The presence of glutamic acid has been confirmed by Edman degradation and characterization of the PTH-amino acid in different solvent systems, and also after regeneration of free amino acid from PTH-amino acid in butanol-acetic acid-water (4:1:5, v/v) system. This is in contrast to the occurrence of aspartic acid or asparagine as N-terminals for several other mammalian thyroglobulins.     

Alternate pleckstrin homology domain orientations regulate dynamin-catalyzed membrane fission

The self-assembling GTPase dynamin catalyzes endocytic vesicle scission via membrane insertion of its pleckstrin homology (PH) domain. However, the molecular mechanisms underlying PH domain–dependent membrane fission remain obscure. Membrane-curvature–sensing and membrane-curvature–generating properties have been attributed, but it remains to be seen whether the PH domain is involved in either process independent of dynamin self-assembly. Here, using multiple fluorescence spectroscopic and microscopic techniques, we demonstrate that the isolated PH domain does not act to bend membranes but instead senses high membrane curvature through hydrophobic insertion into the membrane bilayer. Furthermore, we use a complementary set of short- and long-distance Förster resonance energy transfer approaches to distinguish PH-domain orientation from proximity at the membrane surface in full-length dynamin. We reveal, in addition to the GTP-sensitive “hydrophobic mode,” the presence of an alternate, GTP-insensitive “electrostatic mode” of PH domain–membrane interactions that retains dynamin on the membrane surface during the GTP hydrolysis cycle. Stabilization of this alternate orientation produces dramatic variations in the morphology of membrane-bound dynamin spirals, indicating that the PH domain regulates membrane fission through the control of dynamin polymer dynamics.     

Hypothermia resulting in characteristic ECG changes mimicking an acute myocardial infarction: Osborn waves and atrial fibrillation

Hypothermia can cause several ECG changes which can be mistaken for other cardiac diseases, most importantly acute transmural ischaemia. These ECG changes correlate strongly with the degree of hypothermia and the prognosis of the patient. This brief report presents a 32-year-old male who was seen after a drowning accident. After resuscitation a 12-lead electrocardiogram showed changes typical for hypothermia: atrial fibrillation and Osborn waves. The ECG of the patient normalised after rewarming.     

Porcine big gastrin: Sequence,synthesis, and immunochemical studies

The synthesis of the tetracontapeptide corresponding to a revised sequence for porcine big gastrin is described. Both the synthetic and natural material were identical by radioimmunoassay using L33 antiserum, which is specific for the N-terminal region of the sequence.     

Effect of N-bromosuccinimide-modification of tyrosine side chains of cardiotoxin II of the Indian cobra on biological activity

The essential role of tyrosine residue(s) of cardiotoxin II in the biological activity of the toxin was evaluated using N-bromosuccinimide. N-bromosuccinimide effected oxidation of the tyrosine residues in cardiotoxin II with enhancement in absorbance at 260 nm. The influence of various solvent media such as acetate-formate buffer (pH 4.0), 0.01 N H₂SO₄ (pH 2.0) and Tris-HCl buffer (pH 8.5) on oxidation of tyrosine residues was exa mined. In comparison with 0.01 N H₂S O₄, acetate-formate buffer could prevent secondary oxidations as revealed by lower consumption of oxidant, N-bromosuccinimide, to achieve oxidation. In Tris-HCl buffer oxidation of tyrosine did not take place effectively. N-iodo-succinimide caused only limited oxidation as evident from minor increase in absorbance at 260 nm. N-chlorosuccinimide was completely ineffective. Oxidation of cardiotoxin II with 3.75 equivalents of N-bromosuccinimide tyrosine residue led to complete loss of lethal activity. However, the derivative retained the ability to protect bacterial protoplasts from lysis in solutions of low tonicity. Unlike cardiotoxin II oxidized with N-chlorosuccinimide (50 equivalents/mol of toxin) which retained lethal activity as well as the ability to protect protoplasts from lysis, performic acid-oxidized toxin had lost both the activities.     

Isolation and primary structure of adrenocorticotropin from several species of whale.

The isolation of adrenocorticotropin (ACTH) from fin (Balaenoptera physalus), sei (Blaenoptera borelis) and sperm (Physeter catodon) whale pituitaries is described. Their primary structures have been elucidated by the fluorescein isothiocyanate method and revealed to be identical to the structure of the human hormone. Fin whale exhibited an identical steroidogenic activity to that of the porcine hormone.     

A theoretical study of the structures of (Gly-Pro-Leu)n and (Gly-Leu-Pro)n

Theoretical conformation studies have been carried out for the polytripeptides (Gly-Pro-Leu)n and (Gly-Leu-Pro)n and the Fourier transforms of the structures have been calculated. X-ray powder patterns of these polymers had indicated that both these polymers take up coiled-coil triple-helical structures, but in the case of (Gly-Pro-Leu)n it was not clear whether the triple helix is formed by three parallel polypeptide chains or by a single chain folding back on itself (Scatturin et al 1975). Our studies show that both the polytripeptides can take up stereochemically satisfactory triple-helical structures with three parallel chains. There is also very good agreement between the calculated intensity distribution and that of the observed X-ray pattern, in each case.