Sorbistin, a new aminoglycoside antibiotic complex of bacterial origin. II. Isolation and taxonomy of sorbistin-producing organism

The sorbistin-producing organism Pseudomonas sorbicinii nov. sp. has been isolated from a soil sample by psychrophilic pre-incubation technique. The organism resembles P. fluorescens in many respects but differs in some of the important physiological characteristics such as oxidase production, media specificity for the production of fluorescent pigment, and carbohydrate utilization pattern. The type strain No. D946-B83, has been deposited under the numbers ATCC 31086 and FERM-P 3328.

Interaction of diiodo-L-tyrosine and triiodophenol with bovine serum albumin. Circular dichroism and fluorescence studies

As a model study to investigate the binding mechanism between thyroid hormones and carrier protein, the interaction of diiodo-L-tyrosine (DIT) and triiodophenol (I3phi) with bovine serum albumin (BSA) was investigated by circular dichroism (CD) and fluorescence methods. In both the DIT-BSA system and the I3phi-BSA system, induced Cotton effect was observed in the wavelength region near 320 nm. This induced Cotton effect was measured at various molar ratios of ligands to BSA (L/P). The value of the ellipticity at 319 nm, [theta]319, in the I3phi-BSA system was remarkably large compared with that of the DIT-BSA system, and [theta]319 at an L/P ratio of one was -1.96 X 10(4) (degree cm2 decimole-1) for the I3phi-BSA system and -0.1 X 10(4) for the DIT-BSA system. The binding constants for the combination of BSA with a single molecule of ligand, calculated by measuring the quenching of the fluorescence of the protein, were 1.33 X 10(5) M(-1) at 15 degrees for the DIT-BSA system and 1.6 X 10(9) M(-1) at 28 degrees for the I3theta-BSA system. These results suggest that the binding of I3theta to BSA is stronger than that of DIT and a cleft may exist more congruent with the molecular dimensions of I3theta than with those of DIT.

Conformational analysis of polynucleotides. I. The favorable left-handed helical model for the poly(8,2'-S-cycloadenylic acid) with high anti conformation

1) Energy calculations have shown that poly (8,2'-S-cycloadenylic aicd) can form left-handed helices owing to the high anti conformation. 2) Two favorable left-handed helices are characterized by axial translation per residue (Z=4.3 and 3.6A) and by rotations per residue (theta= 40 degrees and -25 degrees). 3) The proposed helical models might be stable in aqueous solution and is well explicable of the optical property of this compound.

Structural studies on the two forms of 8-bromo-2',3'-O-isopropylideneadenosine

The crystal and molecular structures of two forms of 8-bromo-2',3'-O-isopropylideneadenosine have been determined by X-ray methods. In one form, the molecular structure has planar conformation in the sugar moiety and no intramolecular hydrogen bond. On the other hand, the molecular structure of the second form has C(2')-endo conformation and an intramolecular hydrogen bond. No stacking interaction between adjacent bases is found in either form, but two modes of the base-pairing hydrogen bond exist in the second form.

Fluorescence polarization studies on the local conformation of yeast tRNA

The effects of temperature and guanidine hydrochloride (GuHC1) on the fluorescence polarization of Y base in partially purified yeast phenylalanine tRNA (p.p.tRNAPhe) and in acriflavine conjugates of crude yeast tRNA were investigated to elucidate the stability of the conformation at the 3'-CpCpA terminus and the anticodon loop of tRNA. The results can be summarized as follows: (1) The kinetic unit of the internal rotational motion near Y base in the anticodon loop of p.p.tRNAPhe seems to be independent of the temperature over the range 5--60degrees. Accelerated depolarization is observed in the 3'-CpCpA terminus at temperatures over 30degrees. This suggests that a change occurs in the native conformation of the 3'-CpCpA-acriflavine terminus at temperatures over 30degrees. (2) The fluorescence polarization of Y base in p.p.t-RNAPhe is not affected by the addition of GuHC1 up to 6 M, while that of acriflavine conjugated to the 3'-CpCpA terminus decreases markedly in the presence of 0.8 M GuHC1 reflecting the disruption of the native conformation. These results indicate that the local conformation near Y base is stable, but that of the amino acid acceptor terminus is not.

A model for oscillating chemical reactions

A simple theoretical model for a class of oscillating chemical reactions is investigated, which is inspired by Degn's analysis of the mechanism of Belousov-Zhabotinsky reactions. Although the model involves only one auto-catalytic path, as distinct from models presented hitherto, a limit-cycle behaviour is found for the concentrations, corresponding to a definite region in the space of controllable parameters. Characteristics of the coherent oscillations are investigated together with the behaviour in the induction period. The critical slowing-down around the onset of instability is shown to behave very much like that found in the equilibrium phase transition. The existence of an "anti-Curie" point is found as well as the Curie point, corresponding to the fact that the domain for sustained oscillation is closed in certain directions. Possible extensions of the model and ways of improving the theory are discussed.

The binding of thyroid hormones to bovine serum albumin as measured by circular dichroism

The circular dichroism (CD) spectra of 3,5,3'-triiodothyronine-bovine serum albumin (T3-BSA) and thyroxine-bovine serum albumin (T4-BSA) complexes were measured at the various ratios of T3 or T4 to BSA (T/P) in the wavelength region of 200-350 nm. No spectral change was observed in the chromophoric wavelength region of 250-350 nm. The value of [omicron] at 319 nm of the induced Cotton effect increased with increase of the T/P ratio in both complexes, and in T4-BSA complex, it increased remarkably. The number of thyroid hormone molecules bound to one BSA molecule was estimated to be one in the case of T4-BSA complex and four to five in T3-BSA.