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A Allerhand

Publications and source records attributed to A Allerhand.

45 records · Page 3Linked to original sources
PubMed1973

Natural abundance carbon-13 nuclear magnetic resonance spectra of human serum lipoproteins.

Human serum lipoproteins have been studied by Fourier transform nuclear magnetic resonance of carbon-13 in natural abundance. Spectra of highdensity, low-density, and very-low-density lipoproteins were recorded and partly assigned. The prominent features of these spectra reflect the qualitative and quantitative composition of the lipid moiety of these complexes. The results suggest that carbon-13 nuclear magnetic resonance will be a useful technique for studies of the structural and dynamic parameters of lipoproteins.

Carbon Isotopes↗
PubMed1973

Cytochrome c: observation of numerous single-carbon sites of the reduced and oxidized species by means of natural-abundance 13C nuclear magnetic resonance spectroscopy.

Proton-decoupled, natural-abundance (13)C nuclear magnetic resonance spectra (obtained at 15.18 MHz by the Fourier transform method) of aqueous ferrocytochrome c, ferricytochrome c, and mixtures of both species were recorded. The 18 nonprotonated aromatic carbons of amino-acid residues and the 16 nonprotonated aromatic carbons of the heme yielded 22 narrow single-carbon resonances and 6 narrow two-carbon resonances in the spectrum of ferrocytochrome c. Only some of these resonances were detected in the spectrum of ferricytochrome c. Fast electron transfer between ferrocytochrome c and ferricytochrome c produced chemical exchange effects in spectra of mixtures of the two species: 16 nonprotonated aromatic carbons yielded narrow exchange-averaged resonances as a consequence of their small natural linewidths in both redox states and the small changes in their chemical shifts (relative to the reciprocal of the lifetime between electron exchange) when going from the reduced to the oxidized species. These peaks were assigned to carbons situated far from the iron atom. Their fast exchange behavior was used to establish a one-to-one correspondence between resonances in spectra of the two redox states. The other 18 nonprotonated aromatic carbons yielded exchange-broadened resonances as a consequence of large chemical-shift differences between the diamagnetic and paramagnetic species, and/or large paramagnetic broadening of the resonances of ferricytochrome c. We assigned these resonances (only one of which was identified in the spectrum of ferricytochrome c alone) to carbons that are near the iron atom: C(zeta) of Tyr 67, C(gamma) of His 18, and the 16 nonprotonated carbons of the porphyrin ring. Tentative specific assignments for C(zeta) of Tyr 67 (in the spectra of both redox forms) and for C(zeta) of His 18 (in the spectrum of ferrocytochrome c) are also presented.

Amino Acids↗
PubMed1972

Natural-abundance carbon-13 Fourier-transform nuclear magnetic resonance spectra and spin lattice relaxation times of unfractionated yeast transfer-FNA.

High-resolution Fourier-transform nuclear magnetic resonance at 15.18 MHz was used to observe the proton-decoupled natural-abundance (13)C spectra of aqueous unfractionated tRNA from baker's yeast in the presence of Mg(+2) (8 ions per tRNA molecule), as a function of temperature in the range of 27-82 degrees C. The spectrum of thermally denatured tRNA at 82 degrees C showed numerous sharp resonances, which were assigned to specific types of carbon atoms by comparison with the (13)C spectra of mononucleotides. Only the resonance of carbon 4' of the ribose rings was appreciably shifted (by about 1.5 ppm upfield) with its average position in the mononucleotides. This effect was also seen in the spectrum of poly(A). In the spectrum of folded tRNA (52 degrees C), carbon 4' was further shifted upfield by about 1.5 ppm, and carbons 2' and 3', which yielded a single resonance at 82 degrees C, now showed two partly resolved peaks. The variation of linewidths with temperature (200 mg/ml of tRNA) was gradual in the range 27-82 degrees C, and did not reflect the expected unfolding behavior of tRNA. Moreover, dilution to 80 mg/ml at 27 degrees C had the same effect as an increase in temperature to about 45 degrees C. The line-width changes below 60 degrees were ascribed to tRNA aggregation. In contrast to the behavior of the linewidths, the (13)C spin-lattice relaxation times (T(1)) of individual ribose carbon atoms, measured by means of partially relaxed Fourier-transform spectra were practically independent of temperature up to about 60 degrees C, and increased rapidly at higher temperatures. The T(1) values indicated that the backbone of thermally denatured tRNA is undergoing rapid segmental motion, with an effective correlation time of (2.6 +/- 0.5) x 10(-10) sec. The T(1) values of folded tRNA yielded no evidence of segmental motion. The correlation time for overall rotational reorientation is about (3 +/- 1) x 10(-8) sec in the range 35-54 degrees C. Within experimental error, the T(1) values of methine carbons of the bases were equal to those of the methine carbons on the backbone at all temperatures. Only an upper limit to the rate of internal rotation of the bases could be established.

Adenine Nucleotides↗
PubMed1971

Assignments in the carbon-13 nuclear magnetic resonance spectra of vitamin B12' coenzyme B12' and other corrinoids: application of partially-relaxed fourier transform spectroscopy.

High-resolution Fourier transform NMR at 15.08 MHz was used to observe the proton-decoupled natural-abundance (13)C spectra of aqueous solutions of cobinamide dicyanide (0.067 M), cyanocobalamin (0.024 M), dicyanocobalamin (0.14 M), and coenzyme B(12) (0.038 M). Assignments were made with the aid of chemical shift comparisons, off-resonance single-frequency proton decoupling, partially-relaxed Fourier transform spectra, and splittings arising from (13)C-(31)P coupling. As expected, the (13)C spectra of the coronoids were appreciably more informative than the corresponding proton spectra. Nearly all the lines in the (13)C spectra of the corrinoids were well-resolved single-carbon resonances, in spite of the structural complexity. Partially relaxed (13)C Fourier transform NMR spectra, which yield spin-lattice relaxation times of each resolved resonance, were found to be a very useful addition to the arsenal of NMR techniques.

Carbon Isotopes↗
PubMed1970

Carbon-13 Fourier transform nuclear magnetic resonance. II. Ribonuclease.

High-resolution Fourier transform nuclear magnetic resonance was used to observe the natural abundance (13)C spectrum of a 0.02 M solution of bovine pancreatic ribonuclease A. Peaks assignable to only three carbons were easily observed after 10 hr of signal averaging. A number of tentative assignments were made. As expected, the (13)C spectrum was appreciably richer in detail than the corresponding proton spectrum. Natural abundance (13)C Fourier transform nmr appears to be a practical tool for the study of biopolymers in solution.

Animals↗