Gas chromatographic-mass spectrometric profile of organic acids in urine and serum of diabetic ketotic patients

The organic acids in the urine and serum of diabetic patients with ketoacidosis and disturbance of consciousness were studied using acidification, extraction, evaporation, methoxime formation and trimethylsilylation, gas chromatographic separation and mass spectrometric identification procedures. The organic acid profile of 1 ml of serum ultrafiltrate was obtained with good separation using a gas chromatograph equipped with a glass capillary column and a splitless injector. 5-Hydroxyhexanoic acid and 3-hydroxyvaleric acid were identified for the first time in the urine of diabetic patients with ketoacidosis. Urinary excretion and serum concentrations of 2,3-dideoxypentonic acid were increased in diabetic patients.     

Structural changes of poly-L-lysine in solution and lyophilized form

Two structural changes of poly-l-lysine have been studied by various spectroscopic techniques; one is a structural change of a random coil sample in solution to a mixture of alpha-helix and beta-sheet during rapid freezing in the lyophilizing process, and the other is a pressure-induced structural change from an alpha-helix to a beta-sheet structure for a lyophilized sample.     

Determination of pheophytinatonickel(II) by reversed-phase highperformance liquid chromatography

Summary HPLC determination of pheophytinatonicke(II) (Pheo-Ni) prepared by the replacement of magnesium(II) in chlorophyll with nicke(II) is described. The good separation of PheoNi was obtained by using chemically bonded C₁₈ as the stationary phase and acetone-methanol (50∶50, vol/vol) as the mobile phase. Conventional spectrophotometric method was also used for the determination of PheoNi. For the synthetic samples prepared by mixing (pheophytinato a) nicke(II) [(Pheo-a) Ni] and (pheophytinato b) nicke(II) [(Pheo-b) Ni], analytical values obtained by the spectrophotometric method were very high compared to those obtained by HPLC. In the proposed HPLC method, (Pheo-a) Ni and (Pheo-b). Ni could be determined in the concentration range of 0.028–30μg/ml and 0.038–30μg/ml with relative standard deviations (n=10) of 3.1% and 0.8%, respectively.     

Structure-activity relationships of neuromedin U. V. study on the stability of porcine neuromedin U-8 at the C-terminal asparagine amide under mild alkaline and acidic conditions

Porcine neuromedin U-8 (X-Asn-NH(2), X=H-Tyr-Phe-Leu-Phe-Arg-Pro-Arg) is occasionally unstable in the biological fluids used for bioassay as well as in the acidic solutions used for purification of synthetic peptides. In this study, HPLC examination of an incubate solution of X-Asn-NH(2) revealed that the main decomposition products in Tyrode's solution (pH 7.4) were either alpha- or beta-monocarboxylic acid analogs (X-Asn-OH or X-Asp-NH(2)), and that no dicarboxylic acid analog (X-Asp-OH) was produced. Further investigation, employing a model peptide (Y-Asn-NH(2), Y=Benzoyl-Pro-Arg) incubated in a 0.1 M sodium bicarbonate solution at 60 degrees C, revealed that the decomposition of C-terminal Asn-NH(2) occurred through the formation of an aminosuccinimide intermediate (Y-Asu), at a rate faster than that of Y-Asn-Ser peptide but slower than that of Y-Asn-Gly peptide. Mild acid hydrolysis of X-Asn-NH(2) examined in a 1 M HCl solution at 60 degrees C yielded X-Asn-OH and X-Asp-NH(2), which further decomposed to yield X-Asp-OH. The C-terminal degradation of X-Asn-NH(2) resulted in reduced biological and immunochemical binding activities.     

Assessment of density functional theory to calculate the phase transition pressure of ice

To assess the accuracy of density functional theory (DFT) methods in describing hydrogen bonding in condensed phases, we benchmarked their performance in describing phase transitions among different phases of ice. We performed DFT calculations of ice for phases Ih, II, III, VI and VII using BLYP, PW91, PBE, PBE-D, PBEsol, B3LYP, PBE0, and PBE0-D, and compared the calculated phase transition pressures between Ih-II, Ih-III, II-VI, and VI-VII with the 0 K experimental values of Whalley [J. Chem. Phys., 1984, 81, 4087]. From the geometry optimization of many different candidates, we found that the most stable proton orientation as well as the phase transition pressure does not show much functional dependence for the generalized gradient approximation and hybrid functionals. Although all these methods overestimated the phase transition pressure, the addition of van der Waals (vdW) correction using PBE-D and PBE0-D reduced the transition pressure and improved the agreement for Ih-II. On the other hand, energy ordering between VI and VII reversed and gave an unphysical negative transition pressure. Binding energy profiles of a few conformations of water dimers were calculated to understand the improvement for certain transitions and failures for others with the vdW correction. We conclude that vdW dispersion forces must be considered to accurately describe the hydrogen bond in many different phases of ice, but the simple addition of the R(-6) term with a small basis set tends to over stabilize certain geometries giving unphysical ordering in the high density phases.     

Sterilization of Bacillus spores by converted X rays

Relative sensitivities of endospores of Bacillus pumilus E601, B. subtilis IAM1069, B. megaterium S31 and B. brevis S5 to gamma rays, converted X rays (bremsstrahlung) and electron beams were examined in order to estimate the conditions in which converted X rays kill Bacillus spores. The radiation sensitivities to gamma rays and electron beams of each strain dried on glass fiber filter without additives were found to be almost equivalent, and D values were obtained as follows: 1.5–1.6 kGy for B. pumilus, 1.4–1.5 kGy for B. subtilis, 1.9–2.0 kGy for B. megaterium and 1.6–2.0 kGy for B. brevis. The radiation sensitivities of endospores of each strain to electron beams were slightly lower than those to gamma rays in the dry condition with additives of 2% peptone + 1 % glycerin on glass fiber filters. The increase of radiation resistance in the presence of additives was also observed with X rays, and it was on an intermediate level between those with gamma rays and electron beams. In the dry condition using cellulose filter paper, only the radiation resistances of B. megaterium and B. brevis in the presence of additives B. megaterium and B. brevis in the presence of additives were increased.     

C?H Bond Activation/Borylation of Furans and Thiophenes Catalyzed by a Half‐Sandwich Iron N‐Heterocyclic Carbene Complex

A coordinatively unsaturated iron‐methyl complex having an N‐heterocyclic carbene ligand, [Cp*Fe(L^Me)Me] ( 1 ; Cp*=η⁵‐C₅Me₅, L^Me=1,3,4,5‐tetramethyl‐imidazol‐2‐ylidene), is synthesized from the reaction of [Cp*Fe(TMEDA)Cl] (TMEDA=N,N,N′,N′‐tetramethylethylenediamine) with methyllithium and L^Me. Complex 1 is found to activate the C? H bonds of furan, thiophene, and benzene, giving rise to aryl complexes, [Cp*Fe(L^Me)(aryl)] (aryl=2‐furyl ( 2 ), 2‐thienyl ( 3 ), phenyl ( 4 )). The C? H bond cleavage reactions are applied to the dehydrogenative coupling of furans or thiophenes with pinacolborane (HBpin) in the presence of tert‐butylethylene and a catalytic amount of 1 (10 mol % to HBpin). The borylation of the furan/thiophene or 2‐substituted furans/thiophenes occurs exclusively at the 2‐ or 5‐positions, respectively, whereas that of 3‐substituted furans/thiophenes takes place mainly at the 5‐position and gives a mixture of regioisomers. Treatment of 2 with 2 equiv of HBpin results in the quantitative formation of 2‐boryl‐furan and the borohydride complex [Cp*Fe(L^Me)(H₂Bpin)] ( 5 ). Heating a solution of 5 in the presence of tert‐butylethylene led to the formation of an alkyl complex [Cp*Fe(L^Me)CH₂CH₂tBu] ( 6 ), which was found to cleave the C? H bond of furan to produce 2 . On the basis of these results, a possible catalytic cycle is proposed.