@article {2129, title = {Mixing schemes in a urea-H2O system: A differential approach in solution thermodynamics}, journal = {Journal of Physical Chemistry B}, volume = {112}, number = {36}, year = {2008}, note = {ISI Document Delivery No.: 345EVTimes Cited: 5Cited Reference Count: 29Koga, Yoshikata Miyazaki, Yuji Nagano, Yatsuhisa Inaba, Akira}, month = {Sep}, pages = {11341-11346}, type = {Article}, abstract = {The excess partial molar enthalpies of urea (UR), H-UR(E), were experimentally determined in UR-H2O at 25 degrees C. The H-UR(E) data were determined accurately and in small increments in the mole fraction of UR, X-UR, up to X-UR approximate to 0.22. Hence it was possible to evaluate one more X-UR-derivative graphically Without resorting to any fitting function, and the model-fi-ee UR-UR enthalpic interaction, H{\textquoteright}U{\textquoteright}-R-uR, was calculated. Using previous data for the excess chemical potential, mu(E)(UR), the entropy analogue, S-UR(E)-UR. was also calculated. The X-UR-dependences of both H-UR(E)-UR and S-UR(E)-UR indicate that there is a boundary at X-UR approximate to 0.09 at which the aggregation nature of urea changes. Front the results of our earlier works, we suggest that a few UR molecules aggregate at X-UR approximate to 0.09, while the integrity of H2O is retained at least up to X-UR approximate to 0.20. Together with the findings from our previous studies, we suggest that in the concentration range X-UR < 0.22, UR or its aggregate form hydrogen bonds to the H2O network, reducing the degree of fluctuation characteristic to liquid H2O. However, up to at least X-UR = 0.20 the hydrogen bond network remains intact. Above X-UR approximate to 0.22, the integrity of H2O is likely be lost. Thus, in discussing the effect of urea on H2O and in relating it to the Structure and function of biopolymers in aqueous solutions, the concentration region in question must be specified.}, keywords = {25-DEGREES-C, AQUEOUS UREA, DYNAMICS, ENTHALPIES, H2O, LIQUID WATER, MOLECULAR-ORGANIZATION, NUCLEAR-MAGNETIC-RESONANCE, POTASSIUM, WATER-STRUCTURE}, isbn = {1520-6106}, url = {://000258979800023}, author = {Koga,Yoshikata and Miyazaki, Y. and Nagano, Y. and Inaba, A.} } @article {4901, title = {Monomethylarsonous acid (MMA(III)) is more toxic than arsenite in Chang human hepatocytes}, journal = {Toxicology and Applied Pharmacology}, volume = {163}, number = {2}, year = {2000}, note = {ISI Document Delivery No.: 295TBTimes Cited: 294Cited Reference Count: 28}, month = {Mar}, pages = {203-207}, type = {Article}, abstract = {Methylation has been considered to be the primary detoxication pathway of inorganic arsenic. Inorganic arsenic is methylated by many, but not all animal species, to monomethylarsonic acid (MMA(V)), monomethylarsonous acid (MMA(III)), and dimethylarsinic acid (DMA(V)). The As-V derivatives have been assumed to produce low toxicity, but the relative toxicity of MMA(III) remains unknown. In vitro toxicities of arsenate, arsenite, MMA(V), MMA(III) and DMA(V) were determined in Chang human hepatocytes, Leakage of lactate dehydrogenase (LDH) and intracellular potassium (K+) and mitochondrial metabolism of the tetrazolium salt XTT were used to assess cytotoxicity due to arsenic exposure. The mean LC50 based on LDH assays in phosphate media was 6 mu M for MMA(III) and 68 mu M for arsenite. Using the assay for K+ leakage in phosphate media, the mean LC50 was 6.3 mu M for MMA(III) and 19.8 mu M for arsenite. The mean LC50 based on the XTT assay in phosphate media was 13.6 mu M for MMA(III) and 164 mu M for arsenite. The results of the three cytotoxicity assays (LDH, K+, and XTT) reveal the following order of toxicity in Chang human hepatocytes: MMA(III) > arsenite > arsenate > MMA(V) = DMA(V). Data demonstrate that MMA(III) an intermediate in inorganic arsenic methylation, is highly toxic and again raises the question as to whether methylation of inorganic arsenic is a detoxication process. (C) 2000 Academic Press.}, keywords = {ARSENATE, ARSENITE, ASSAY, CELLS, Chang human hepatocytes, DIMETHYLARSINIC ACID, DMA, DMA(V), DMPS, ENZYMATIC METHYLATION, LDH, LIVER, MICE, MMA(III), MMA(V), monomethylarsonic acid, MONOMETHYLARSONOUS ACID, POTASSIUM, VIABILITY, XTT}, isbn = {0041-008X}, url = {://000085983000013}, author = {Petrick, J. S. and Ayala-Fierro, F. and Cullen, W. R. and Carter, D. E. and Aposhian, H. V.} } @article {2874, title = {AN ENANTIOSPECIFIC SYNTHESIS OF 4-METHYLCAMPHOR}, journal = {Tetrahedron-Asymmetry}, volume = {4}, number = {11}, year = {1993}, note = {ISI Document Delivery No.: MJ468Times Cited: 10Cited Reference Count: 38}, month = {Nov}, pages = {2363-2370}, type = {Article}, abstract = {Treatment of (-)-2-methylenebornane (7), derived from (+)-camphor (1), with 45\% HBr /HOAc results in Wagner-Meerwein rearrangement and formation of 4-methylisobornyl bromide (17) in 80-90\% yield. The enantiopurity of (17) was determined by conversion to (+)-4-methylisoborneol (5) and (-)-4-methylcamphor (3).}, keywords = {CAMPHOR DERIVATIVES, ESTERS, KETONES, NATURAL PRODUCT SYNTHESIS, POTASSIUM, REARRANGEMENTS, ROUTE, STEROID-SYNTHESIS, SYNTHONS}, isbn = {0957-4166}, url = {://A1993MJ46800024}, author = {Money, T. and Palme, M. H.} }