Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Optical Rotatory Dispersion”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,693 records · Page 94Linked to original sources
PubMed1998

The similarity of action spectra for thymine dimers in human epidermis and erythema suggests that DNA is the chromophore for erythema.

The location of DNA photodamage within the epidermis is crucial as basal layer cells are the most likely to have carcinogenic potential. We have determined the action spectra for DNA photodamage in different human epidermal layers in situ. Previously unexposed buttock skin was irradiated with 0.5, 1, 2, and 3 minimal erythema doses of monochromatic UVR at 280, 290, 300, 310, 320, 340, and 360 nm. Punch biopsies were taken immediately after exposure and paraffin sections were prepared for immunoperoxidase staining with a monoclonal antibody against thymine dimers that were quantitated by image analysis. Dimers were measured at two basal layer regions, the mid and the upper living epidermis. The slopes of dose-response curves were used to generate four action spectra, all of which had maxima at 300 nm. Dimer action spectra between 300 and 360 nm were independent of epidermal layer, indicating comparable epidermal transmission at these wavelengths. Furthermore, we observed 300 nm-induced dimers in dermal nuclei; however, there was a marked effect of epidermal layer between 280 and 300 nm, showing relatively poor transmission of 280 and 290 nm to the basal layer. These data indicate that solar UVB (approximately 295-320 nm) is more damaging to basal cells than predicted from transmission data obtained from human epidermis ex vivo. The epidermal dimer action spectra were compared with erythema action spectra determined from the same volunteers and ultraviolet radiation sources. Overall, these spectral comparisons suggest that DNA is a major chromophore for erythema in the 280-340 nm region.

Adult↗
PubMed1977

Stability of segments of rabbit alpha-tropomyosin.

Rabbit alpha-tropomyosin was cleaved into two pieces at the cysteine residue of each chain. The products were separated by chromatography and characterized by amino acid analysis, molecular weight determination in benign and denaturing solvents, optical rotation and circular dichroism. When the cleavage reaction was carried out under mild conditions which preserve the two-chain structure there was considerable loss of alpha-helix in each segment. Thermal stability studies, monitored by optical rotation and circular dichroism, showed that the transition temperature of the N-terminal fragment at pH 7.6 was approximately 17 degrees C higher than that of the C-terminal fragment. In acid solutions there is little difference in the thermal stability of the two segments. The least stable part of the molecule is concluded to be between residues 133 and 205 and this includes the troponin-binding site. The relative stabilities found for segments of rabbit alpha-tropomyosin differ from recent published conclusions and this may be a result of the different methods used to study the loss of the alpha-helical conformaton. The two tropomyosin fragments, unlike the parent tropomyosin, do not inhibit actomyosin adenosinetriphosphatase when mixed with troponin. The fragments did not show any of the aggregation properties of tropomyosin and did not combine with actin. The N-terminal fragment did not complex with troponin but there was some evidence for an interaction between the C-terminal fragment and troponin.

Actins↗
PubMed1969

Preparation of four new antibiotics from a mutant of Streptomyces fradiae.

A mutant of Streptomyces fradiae 3535 incapable of synthesizing the antibiotic neomycin in the absence of added deoxystreptamine, the aminocyclitol subunit of the antibiotic, has been isolated from a culture treated with N-methyl-N'-nitro-N-nitrosoguanidine. The related aminocyclitols streptamine and 2-epistreptamine, both available by chemical synthesis, were incorporated by the mutant strain into four new antibiotics, for which we suggest the names hybrimycins A (isomers 1 and 2, from streptamine) and hybrimycins B (isomers 1 and 2, from 2-epistreptamine). Structures of the new antibiotics were established from the mass spectral, nuclear magnetic resonance, and optical rotatory properties of appropriate derivatives. This method offers a promising approach to the synthesis of other antibiotics.

Anti-Bacterial Agents↗