1.Applications of the CSA-amplified PASS experiment.
Orr RM1, Duer MJ. Solid State Nucl Magn Reson. 2006 Jul;30(1):1-8. Epub 2006 Jan 6.
The recently reported CSA-amplified PASS experiment correlates the spinning sidebands at the true spinning frequency omega(r) with the spinning sidebands that would be obtained at the effective spinning frequency omega(r)/N, where N is termed the scaling factor. The experiment is useful for the measurement of small chemical shift anisotropies, for which slow magic-angle spinning frequencies, required to measure several spinning sidebands, can be unstable. We have experimentally evaluated the reliability of this experiment for this application. In particular we have demonstrated that large scaling factors of the order of N=27 may be used, whilst still obtaining accurate chemical shift sideband intensities at the effective spinning frequency from the F(1) projection. Moreover, the sideband intensities are accurately obtained even in the presence of significant pulse imperfections. A second application of the CSA-amplified PASS experiment is the measurement of the chemical shift anisotropy of sites that experience homonuclear dipolar coupling, as may be found in uniformly labelled biological molecules, or for nuclei with a high natural abundance.
2.Study of intravenous hyperalimentation: effect of selected amino acids on the stability of intravenous fat emulsions.
Takamura A, Ishii F, Noro S, Tanifuji M, Nakajima S. J Pharm Sci. 1984 Jan;73(1):91-4.
In an attempt to resolve the conflicts relevant to intravenous fat emulsion compatibility two amino acids, L-valine and L-histidine monohydrochloride monohydrate, were chosen as intravenous additives, and these substances were investigated as to whether they could induce significant changes in the physicochemical properties of an intravenous soybean oil emulsion. The stability of the fat emulsion was evaluated in terms of gross visual observation, particle size distribution, surface tension, pH, and the zeta potential. It was found that (a) no significant difference was produced on the particle size distribution up to 7 d after admixing, (b) the mean diameter of oil globules was approximately 0.21-0.24 micron, and (c) the fat emulsion was sufficiently stable, with a zeta potential ranging between -30 and -60 mV. The relationship of the isoelectric point (pI) of the amino acids and the pH of the buffer solutions was determined to be one of the most important factors in the stability of the fat emulsion.
3.Evidence for histamine involvement in the effect of histidine loads on food and water intake in rats.
Vaziri P1, Dang K, Anderson GH. J Nutr. 1997 Aug;127(8):1519-26.
We examined the hypothesis that histidine is a regulator of short-term food and water intake in rats and that this control is through histidine's action as a precursor for histamine. The primary objectives were to measure food and water intake after histidine monohydrochloride monohydrate (His-HCl) given by intragastric (IG) and intraperitoneal (IP) routes of administration and to measure feeding and drinking responses to histidine when given after blockade of the histaminergic pathway by chlorpheniramine (CPA) and alpha-fluoromethylhistidine (FMH). Eight experiments were conducted using a back-to-back design. Rats were given treatment by IP or IG administration, and food and water intake was measured during time periods of 0-1, 1-2, 2-3 and 3-14 h. Histidine consistently reduced food intake with the sensitivity to IP much greater than to the IG route. The effect of histidine given by IP or IG on water intake was similar, generally causing an increase at least in the first hour.
4.Accurate (13)C and (15)N Chemical Shift and (14)N Quadrupolar Coupling Constant Calculations in Amino Acid Crystals: Zwitterionic, Hydrogen-Bonded Systems.
Strohmeier M1, Stueber D1, Grant DM1. J Phys Chem A. 2003 Sep 25;107(38):7629-42. doi: 10.1021/jp0350114.
EIM (embedded ion method), cluster, combined EIM/cluster, and isolated molecule (13)C and (15)N chemical shielding and quadrupolar coupling constant (QCC) calculations at the B3LYP level with D95**, D95++**, 6-311G**, and 6-311+G** basis sets were done on the amino acids l-alanine, l-asparagine monohydrate, and l-histidine monohydrate monohydrochloride and on the two polymorphs α and γ glycine. The intermolecular interactions that are present in the amino acid crystals are accounted for in the EIM calculations by a finite array of point charges calculated from Ewald lattice sums and in the cluster calculations by a shell of neighboring molecules or molecular fragments. The combined EIM/cluster calculations utilize a cluster of molecules inside an EIM point charge array. The theoretical (13)C and (15)N principal shielding values for the amino acids studied are compared to the experimental principal shift values. In addition, theoretical CN bond orientations in the chemical shift principal axis system (PAS) are compared to the experimental orientations obtained from (13)C-(14)N dipolar couplings.
