Self-Association of Nicotinamide in Aqueous-Solution: N.M.R. Studies of Nicotinamide and the Mono- and Di-methyl-Substituted Amide Analogs

1993 ◽  
Vol 46 (3) ◽  
pp. 377 ◽  
Author(s):  
WN Charman ◽  
CSC Lai ◽  
DJ Craik ◽  
BC Finnin ◽  
BL Reed
Keyword(s):  
Aqueous Solution ◽  
Lattice Relaxation ◽  
Amide Group ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Self Association ◽  
13C Chemical Shift ◽  
Associated Species ◽  
Monosubstituted Derivative

The concentration-dependent self-association of nicotinamide in solution has been studied by 1H and 13C n.m.r. spectroscopy, attendant relaxation time measurements, and osmometric techniques. N-Methylnicotinamide and N,N- dimethylnicotinamide were also studied to evaluate the role of the amide group in the association process. The osmometric studies indicated that the dimethyl -substituted analogue underwent little (if any) self-association, whereas nicotinamide and N- methylnicotinamide did self-associate. The concentration-dependent 1H and 13C chemical shift profiles of nicotinamide and the monosubstituted analogue indicated that the association involved the amide group and did not occur through stacking of the pyridine rings. Spin lattice relaxation (T1) studies indicated that the T1( ortho C)/T1( para C) ratio of nicotinamide decreased with increasing concentration, and that loss of a preferred axis of rotation had occurred due to formation of a large associated species. The T1 ratios of either substituted amide analogue were not concentration-dependent. The extent of self-association of the monosubstituted derivative was insufficient to affect the measured T1 ratios. These data indicate that the self-association of nicotinamide in aqueous solution occurs primarily through interamide hydrogen bonding.

scholarly journals The physical state of osmoregulatory solutes in unicellular algae. A natural-abundance carbon-13 nuclear-magnetic-resonance relaxation study

1982 ◽  
Vol 202 (3) ◽  
pp. 699-706 ◽  
Author(s):  
R S Norton ◽  
M A MacKay ◽  
L J Borowitzka
Keyword(s):  
Aqueous Solution ◽  
Green Alga ◽  
Physical State ◽  
Lattice Relaxation ◽  
Natural Abundance ◽  
Spin Lattice Relaxation ◽  
Paramagnetic Species ◽  
Intact Cells ◽  
Spin Lattice ◽  
Synechococcus Sp

Natural-abundance 13C n.m.r. spin-lattice relaxation-time measurements have been carried out on intact cells of the unicellular blue-green alga Synechococcus sp. and the unicellular green alga Dunaliella salina, with the aim of characterizing the environments of the organic osmoregulatory solutes in these salt-tolerant organisms. In Synechococcus sp., all of the major organic osmoregulatory solute, 2-O-alpha-D-glucopyranosylglycerol, is visible in spectra of intact cells. Its rotational motion in the cell is slower by a factor of approx. 2.4 than in aqueous solution, but the molecule is still freely mobile and therefore able to contribute to the osmotic balance. In D. salina, only about 60% of the osmoregulatory solute glycerol is visible in spectra of intact cells. The rotational mobility of this observable fraction is approximately half that found in aqueous solution, but the data also indicate that there is a significant concentration of some paramagnetic species in D. salina which contributes to the overall spin-lattice relaxation of the glycerol carbon atoms. The non-observable fraction, which must correspond to glycerol molecules that have very broad 13C resonances and that are in slow exchange with bulk glycerol, has not been properly characterized as yet, but may represent glycerol in the chloroplast. The implications of these findings in relation to the physical state of the cytoplasm and the mechanism of osmoregulation in these cells are discussed.

scholarly journals The role of the glassy dynamics and thermal mixing in the dynamic nuclear polarization and relaxation mechanisms of pyruvic acid

2014 ◽  
Vol 16 (48) ◽  
pp. 27025-27036 ◽  
Author(s):  
M. Filibian ◽  
S. Colombo Serra ◽  
M. Moscardini ◽  
A. Rosso ◽  
F. Tedoldi ◽  
...  
Keyword(s):  
Relaxation Rate ◽  
Dynamic Nuclear Polarization ◽  
Pyruvic Acid ◽  
Nuclear Polarization ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Thermal Mixing ◽  
Spin Lattice

In pyruvic acid containing 15 mM trityl below 4 K 13C polarization and spin–lattice relaxation rates are proportional to the spin–lattice relaxation rate of electrons, suggesting an efficient thermal mixing scenario.

The role of the ordinary and anharmonic Raman processes in Rb2PtI6

1978 ◽  
Vol 56 (11) ◽  
pp. 1461-1467 ◽  
Author(s):  
Robert G. C. McElroy ◽  
Robin L. Armstrong
Keyword(s):  
Nuclear Spin ◽  
Lattice Relaxation ◽  
Experimental Results ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Raman Process ◽  
Nuclear Spin Lattice Relaxation ◽  
Rare Opportunity

Measurements of iodine nuclear spin lattice relaxation in Rb2PtI6 provide a rare opportunity to directly measure the separate contributions of the ordinary and anharmonic Raman processes. It is shown that for this crystal one may separately determine W1 and W2 and that these rates may be uniquely related to the two Raman processes. The experimental results show that the anharmonic Raman process is dominant but not to the total exclusion of the ordinary Raman process.

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