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31.
Various cellulose II samples, ball-milled native celluloses and ball-milled wood saw dust were subjected to 2,2,6,6-tetramethypyperidine-1-oxyl
radical (TEMPO)-mediated oxidation to prepare cellouronic acid Na salts (CUAs). The TEMPO-oxidized products obtained were
analyzed by 13C-NMR and size-exclusion chromatography (SEC). When the cellulose II samples with degrees of polymerization (DP) of 220–680
were used as the starting materials, the CUAs obtained had weight-average DP (DPw) values of only 38–79. Thus, significant
depolymerization occurs on cellulose chains during the TEMPO-mediated oxidation. These DP values of CUAs correspond to the
cellulose II crystal sizes along the chain direction in the original cellulose II samples, but not necessarily to their leveling-off
DP values. CUAs can be obtained also from ball-milled native celluloses in good yields by TEMPO-mediated oxidation, although
their DPw values are lower than about 80. On the other hand, CUA with DPw of about 170 was obtained from ball-milled wood
saw dust. 相似文献
32.
33.
Yasuhiro Isogai Anna Ishii Manabu Ishida Masahiro Mukai Motonori Ota Ken Nishikawa Tetsutaro Iizuka 《Journal of Chemical Sciences》2000,112(3):215-221
De novo design of artificial proteins is an essential approach to elucidate the principles of protein architecture and to understand
specific functions of natural proteins and also to yield novel molecules for medical and industrial aims. We have designed
artificial sequences of 153 amino acids to fit the main-chain framework of the sperm whale myoglobin structure based on the
knowledge-based energy functions to evaluate the compatibility between protein tertiary structures and amino acid sequences.
The synthesized artificial globins bind a single heme per protein molecule as designed, which show well-defined electrochemical
and spectroscopic features characteristic of proteins with a low-spin heme. Redox and ligand binding reactions of the artificial
heme proteins were investigated and these heme-related functions were found to vary with their structural uniqueness. Relationships
between the structural and functional properties are discussed. 相似文献
34.
A lower (upper) bound is given for the distribution of each dj, j = k + 1, …, p (j = 1, …, s), the jth latent root of AB?1, where A and B are independent noncentral and central Wishart matrices having with rank and Wp(n, Σ), respectively. Similar bound are also given for the distributions of noncentral means and canonical correlations. The results are applied to obtain lower bounds for the null distributions of some multivariate test statistics in Tintner's model, MANOVA and canonical analysis. 相似文献
35.
The reason for anomalous NMR patterns of cellulose β-ketoesters, which were prepared by reaction between cellulose and ketene
dimers having long alkyl chains (AKDs) under homogeneous conditions using a cellulose solvent system, was studied by molecular
dynamics simulation. Cellulose/AKD β-ketoester models with degree of substitution (DS) 2.0 and degree of polymerization (DP)
5, 10, 20 or 40, and cellulose/fatty acid ester models with DS 3.0 and DP 5, 10, 20 or 40 were assembled in the simulation.
The calculated results were compared with those obtained by NMR and conformation analyses of the actually prepared cellulose
derivatives. The molecular dynamics simulation data showed that the average velocities of anhydroglucose units in cellulose/AKD
β-ketoesters were approximately one tenth of those in cellulose/fatty acid esters. Thus, cellulose chains in the cellulose/AKD
β-ketoesters are extremely restricted in motion by the β-ketoester substituents. The solid-like behavior of cellulose chains
in cellulose/AKD β-ketoesters in solution state is, therefore, explainable by strong restriction in motion of cellulose chains
by long, branched and bulky substituents introduced into cellulose hydroxyls in high densities via β-ketoester bonds. 相似文献
36.
37.
38.
Yamamoto K Isogai Y Sato H Taketomi Y Murakami M 《Analytical and bioanalytical chemistry》2011,400(7):1829-1842
Phospholipase A2 (PLA2) is a group of enzymes that hydrolyze the sn-2 position of glycerophospholipids to yield fatty acids and lysophospholipids. Of many PLA2s or related enzymes identified to date, secreted PLA2s (sPLA2s) comprise the largest family that contains 10 catalytically active isozymes. Besides arachidonic acid released from cellular
membranes for eicosanoid synthesis, several if not all sPLA2s have recently been implicated in hydrolysis of phospholipids in lipoprotein particles. The sPLA2-processed low-density lipoprotein (LDL) particles contain a large amount of lysophospholipids and exhibit the property of
“small-dense” or “modified” LDL, which facilitates foam cell formation from macrophages. Transgenic overexpression of these
sPLA2s leads to development of atherosclerosis in mice. More importantly, genetic deletion or pharmacological inhibition of particular
sPLA2s significantly attenuates atherosclerosis and aneurysm. In this article, we will give an overview of current understanding
of the role of sPLA2s in atherosclerosis, with recent lipidomics data showing the action of a subset of sPLA2s on lipoprotein phospholipids. 相似文献
39.
Takafumi Isogai 《Annals of the Institute of Statistical Mathematics》1989,41(1):169-186
Changes in the joint distribution of influence functions for the mean vector and the covariance matrix are examined when the true probability distribution is contaminated. In particular, the formulas for influence functions of the first and second moments with respect to the above joint distribution are obtained and used to derive reasonable test statistics for multivariate normality. The formulas are extended by using the joint distribution of score functions for population parameters. An application of the extended formulas to the usual linear regression analysis leads to a measure of multivariate skewness which can be used to reduce the effect of non-normality of the response variable. Also, some relationship between the extended formulas and goodness-of-fit statistics is discussed and used to derive test statistics for multivariate normality. 相似文献
40.
Isogai H Kato M Taniguchi Y 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(13):3135-3139
Effects of pressure and solvents on the infrared spectrum of phenol in solutions have been investigated using a hydrostatic high-pressure cell with synthetic diamond windows. For the first time, we performed a quantitative investigation of the effect of pressure on the absolute intensity of O-H stretching mode up to 150 MPa (in CCl4) and 200 MPa (in CS2). For comparison, we measured the effect of solvents on the absorption intensity. The Polo-Wilson theory, which is the most traditional theory for medium effects on the intensity, was tested for present results. The pressure dependence was in sufficient agreement with their formula, while the solvent dependence is unsatisfactory. This suggests that the traditional intensity correction by Polo-Wilson's formula is practically valid for pressure-tuning infrared experiments. 相似文献