127-I]- or carrier-free [125-I]monoiodoinsulin.

Insulin was enzymatically moniodinated with 127-I or 125-I, and an improved method of purification by anion exchange chromatography was employed. (127-I)Monoiodoinsulin was identified by spectrophotometric analysis and its molar extinction coefficient determined to be 6.31 times 10-3 M-1 cm minus 1. The observed specific activity of carrier-free (125-I)monoidoinsulin was close to the theoretical value (378mCi/mg). The monoiodotyrosyl residue of monoidoinsulin was shown to be solvent-exposed. The ionic properties of the substituted hormone were altered at pH values close to the pK of monoiodotyrosine (8.85), but the pI was unchanged (5.65). (127-I)Monoiodoinsulin formed rhombohedral crystals and co-crystallized with native insulin. Monoidoinsulin was indistinguishable from insulin with respect to binding to two out of three guinea pig anti-insulin sera, to binding to IM9 cultured human lymphocytes, and to binding to isolated rat hepatocyte plasma membranes. The potency of monoidoinsulin was not statistically different from that of insulin in the rat fat cell bioassay and in the mouse convulsion assay. An insulin-degrading enzyme extracted from rat liver degraded monoiodoinsulin less readily than native insulin; monoiodoinsulin was a competitive inhibitor of insulin degradation, and the Km values were 30 nM AND 78 NM for monoidoinsulin and native insulin, respectively. It is concluded that monoidination does not markedly alter the three-dimensional structure of the molecule and that only a few sensitive biological systems are able to distinguish the monoidinated from the native hormone.     

Salt effects on bacteriophage T7-I

The thermal denaturation as a measure of the structural stability of the nucleoprotein in bacteriophage T7 has been studied in dependence of the ionic environment. Optical density and circular dichroism melting curves measured at wavelengths characterizing either the DNA or protein conformational changes were compared to identify different steps of the denaturation and to follow the effect of the ions. Monovalent salts strengthen the helical structure of intraphage DNA logarithmically in the way as they do in the case of isolated double-stranded DNA. Mg2+ and Ca2+ at very low concentrations stabilize the DNA helicity. Higher divalent ion concentrations decrease the stability of the double helix because of the repulsive ionic interactions. The high structural sensitivity of DNA in the presence of Mg2+ and Ca2+ in this "in situ" environment can be related to the biological role of these ions.     

High correlation between prolactinemia, 125-I hLH binding and progesterone secretion by an experimental luteoma

Autoimplantation of an ovary, containing fresh corpora lutea, into the spleen of an ovariectomized rat is followed by strong luteinization and size increase of the grafted gonad. Thus, large amounts of luteal tissue for biochemical studies, and their histological controls are available. Furthermore, progesterone secretion can be easily determined in samples collected from the portal vein. Since prolactin has been implicated in the control of luteal tissue, the role of this hormone on hLH binding and progesterone secretion was determined. Different levels of endogenous serum prolactin were achieved by pharmacological treatments with neurotropic agents. Scatchard plots of 125-I hLH binding data derived from luteoma particulate fractions revealed the presence of one type of binding site with high affinity. At the same time as binding increased, prolactinemia augmented, with a high correlation (R:0.99) between prolactinemia and LH binding. Moreover, progesterone secreted by the luteoma increased as LH binding sites augmented (R:0,97). It is concluded that a high correlation between prolactinemia and LH binding, as well as between this last parameter and progesterone output exists in the experimental luteoma.     

F.T.-I.R. and laser-raman spectra of d-ribose and 2-deoxy-d-erythro-pentose (“2-deoxy-d-ribose”)

Laser-Raman spectra of d-ribose and 2-deoxy-d-erythro-pentose in aqueous solution are reported. F.t.-i.r. and Raman spectra have been obtained for crystals of these sugars. Assignments of the Raman bands observed in solution are proposed. The spectral differences between the two sugars are discussed in terms of the structural difference. The analysis of the frequencies observed permits identification of each of the sugars and their isomeric analogs, and can be used as a basis for study of nucleosides and nucleotides by vibrational spectroscopy.     

Composition and structure of the antibiotic polypeptide 308-I from Actinomadura recticatena

Antibiotic 308-I isolated from Actinomadura recticatena and the products of its degradation were studied with the methods of electron impact mass spectrometry, chemical ionization with ammonia, field desorption and ion extraction from solution under atmospheric pressure. It was shown that by its composition and structure antibiotic 308-I was identical to antibiotic BBM-928 A.