The Rate of Chemical Reactions

Tài liệu The language of Chemistry, Food and Biological Technology in English (ngôn ngữ tiếng anh chuyên ngành công nghệ hóa học, công nghệ thực phẩm và công nghệ sinh học) - GS.TS. Nguyễn Thị Hiền (chủ biên) có cấu trúc gồm 4 part. Phần 1 của Tài liệu trình bày những nội dung sau: The basic units, Chemistry and Its Branches, Classification of Matter, Isolation and Purification of Substances, The Rate of Chemical Reactions, Equipments of Chemical Laboratory, Relationship of Chemical Industry to Other Industries, The Laboratory Not Tài liệu, Study Outline of Chemistry.

89p cobetocxul9 21-05-2015 145 25   Download

The high-pressure stopped-flow technique is applied to study the CO binding in cytochrome P450cam (P450cam) bound with homologous substrates (1R-camphor, camphane, norcamphor and norbornane) and in the substrate-free protein. The activation volume DV # of the CO on-rate is positive for P450cam bound with substrates that do not contain methyl groups. The kon rate constant for these substrate complexes is in the order of 3 · 106 M)1Æs)1. In contrast, P450cam complexed with substrates carrying methyl groups show a negative activation volume and a low kon rate constant of % 3 · 104 M)1Æs)1. ...

8p system191 01-06-2013 37 3   Download

The involvement of the lysine residue present at the active site of Ehrlich ascites carcinoma (EAC) cell glyceraldehyde-3-phosphate dehydrogenase (Gra3P DH) was investigated by using the lysine specific reagents trinitrobenzenesulfonic acid (TNBS) and pyridoxal phosphate (PP). Both TNBS and PP inactivated EAC cell Gra3P DH with pseudo-first-order kinetics with the rate dependent on modifier concentration. Kinetic analysis, including a Tsou plot, indicated that both TNBS and PP apparently react with one lysine residue per enzyme molecule.

8p system191 01-06-2013 36 2   Download

Four substrate analogs, 4-(2-naphthyloxy)-2-butyn-1-amine (1), 1,4-diamino-2-chloro-2-butene (2), 1,6-diamino-2,4hexadiyne (3), and 2-chloro-5-phthalimidopentylamine (4) have been tested as inhibitors against mammalian, plant, bacterial, and fungal copper-containing amine oxidases: bovine plasma amine oxidase (BPAO), equine plasma amine oxidase (EPAO), pea seedling amine oxidase (PSAO), Arthrobacter globiformis amine oxidase (AGAO), Escherichia coli amine oxidase (ECAO), and Pichia pastoris lysyl oxidase (PPLO).

14p research12 01-06-2013 43 6   Download

Two genes (CM-AAT1 and CM-AAT2) with strong sequence homology (87% identity at the protein level) putatively involved in the formation of aroma volatile esters have been isolated from Charentais melon fruit. They belong to a large and highly divergent family of multifunctional plant acyl-transferases and show at most 21% identity to the only other fruit acyl-transferase characterized so far in strawberry. RT-PCR studies indicated that both genes were specifically expressed in fruit at increasing rates in the early and mid phases of ripening.

8p research12 01-06-2013 48 4   Download

The human replication protein Cdc6p is translocated from its chromatin sites to the cytoplasm during the replication phase (S phase) of the cell cycle. However, the amounts of Cdc6p on chromatin remain high during S phase implying either that displaced Cdc6p can rebind to chromatin, or that Cdc6p is synthesized de novo. We have performed metabolic labeling experiments and determined that [35S]methionine is incorporated into Cdc6p at similar rates during the G1 phase and the S phase of the cell cycle. Newly synthesized Cdc6p associates with chromatin....

7p research12 01-06-2013 39 3   Download

CTP synthase catalyzes the reaction glutamine + UTP +ATPfiglutamate + CTP + ADP + Pi.The rate of the reaction is greatly enhanced by the allosteric activator GTP.We have studied the glutaminase half-reactionofCTP synthase from Lactococcus lactisand its response to the allosteric activator GTP and nucleotides that bind to the active site. In contrast to what has been found for the Escherichia colienzyme, GTP activation of the L. lactis enzyme did not result in similarkcat values for the glutami-nase activity and glutamine hydrolysis coupled to CTP synthesis. ...

8p research12 29-04-2013 44 2   Download

Tightly coupled inside-out vesicles were prepared from Paracoccus denitrificanscells (SPP, sub-Paracoccusparticles) and characterized kinetically. The rate of NADHoxidation, catalysed by SPP, increases 6–8 times on addition of gram-icidin. The vesicles are capable of catalysing DlH + -dependent reverse electron transfer fromquinol toNAD + . The kinetic parameters of the NADH-oxidase and the reverse electron transfer carried out by membrane-bound P. denitrificanscomplex I were estimated and compared with those of the mitochondrial enzyme. ...

5p research12 23-04-2013 41 3   Download

The interactions between photosystem I and five charge mutants of plastocyanin from the cyanobacteriumPhormi-dium laminosumwere investigatedin vitro. The dependence of the overall rate constant of reaction,k2, on ionic strength was investigated using laser flash photolysis. The rate con-stant of the wild-type reaction increased with ionic strength, indicating repulsion between the reaction partners. Remov-inganegativechargeonplastocyanin(D44A) acceleratedthe reactionandmade it independentof ionic strength; removing a positive charge adjacent to D44 (K53A) had little effect....

10p tumor12 22-04-2013 38 4   Download

Jurkat T lymphocytes were treated with daunorubicin and WP631, a daunorubicin-based DNAbinding agent, in experiments aimed to analyze cellular uptake of these drugs and their effect on cell viability. WP631 was taken up more slowly than daunorubicin, but laser confocal microscopy and spectrofluorometricquantificationshowed that thedrug accumulated in the cells. Despite the slow uptake rate, the antiproliferative capacity of WP631 (measured as IC50after a 72-h continuous treatment) was greater than that of daunorubicin.

7p tumor12 20-04-2013 39 5   Download

The lysine-binding-site-mediated interaction between plas-min and antiplasmin is of great importance for the fast rate of this reaction. It also plays an important part in regulat-ing the fibrinolytic enzyme system. To identify structures important for its noncovalent interaction with plasmin, we constructed seven single-site mutants of antiplasmin by modifying charged amino acids in theC-terminal part of the molecule.

7p fptmusic 16-04-2013 50 3   Download

The active form of the oxygen sensor fumarate nitrate reductase regulator (FNR) of Escherichia colicontains a [4Fe-4S] cluster which is converted to a [2Fe-2S] cluster after reaction with air, resulting in inactivation of FNR. Reaction of reconstituted [4Fe-4S]ÆFNR with air resulted within 5 min in conversion to apoFNR. The rate was comparable to the rate known for [4Fe-4S]ÆFNR⁄[2Fe-2S]ÆFNR cluster conversion, suggesting that apoFNR is a product of [2Fe-2S]ÆFNR decomposition and a final form of air-inacti-vated FNR in vitro. ...

10p fptmusic 11-04-2013 33 2   Download

The signal transducer and activator of transcription (STAT) proteins have initiallybeendescribedas cytoplasmicproteins that enter the nucleus only after cytokine treatment of cells. Contrary to this assumption, it was demonstrated that STATs are constantly shuttling between nucleus and cyto-plasm irrespective of cytokine stimulation. This happens both via carrier-dependent as well as carrier-independent transportation. Moreover, it was also recognized that cyto-kine stimulation triggers nuclear retention of dimeric STATs, rather than affecting the rate of nuclear import. ...

7p awards 05-04-2013 36 3   Download

Glutamine is an essential amino acid in cancer cells and is required for the growth of many other cell types. Glutami-nase activity is positively correlated with malignancy in tumours andwith growth rate in normal cells. In the present work, Ehrlich ascites tumour cells, and their derivative, 0.28AS-2 cells, expressing antisense glutaminase mRNA, were assayed for apoptosis induced by methotrexate and hydrogen peroxide. It is shown that Ehrlich ascites tumour cells, expressing antisense mRNA for glutaminase, contain lower levels of glutathione than normal ascites cells. In addition, 0.

9p awards 05-04-2013 47 4   Download

Human cytochrome P450 3A4 forms a series of minor testosterone hydroxylation products in addition to 6b-hy-droxytestosterone, the major product. One of these, formed at the next highest rate after the 6b-and 2b-hydroxy prod-ucts, was identified as 1b-hydroxytestosterone. This product was characterized from a mixture of testosterone oxidation products using an HPLC-solid phase extraction-cryoprobe NMR/time-of-flight mass spectrometry system, with an estimated total of
6lgof this product.Mass spectrometry established the formula as C19H29O3(MH + 305.2080)....

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Amino acid biosynthesis and central carbon metabolism of Pichia pastoriswere studied using biosynthetically directed fractional 13 C labeling. Cells were grown aerobically in a chemostat culture fed at two dilution rates (0.05 h )1 , 0.16 h )1 ) with glycerol as the sole carbon source. For investigation of amino acid biosynthesis and comparison with glycerol cultivations, cells were also grown at 0.16 h )1 on glucose. Our results show that, firstly, amino acids are synthesized as inSaccharomyces cerevisiae. ...

9p dell39 03-04-2013 24 2   Download

ThepyrGgene fromLactococcus lactisencodes CTP syn-thase (EC 6.4.3.2), an enzyme converting UTP to CTP. A series of strains were constructed with different levels of pyrGexpression by insertion of synthetic constitutive pro-moters with different strengths in front ofpyrG.These strains expressed pyrGlevels in a range from 3 to 665% relative to thewild-type expression level.Decreasing the level of CTP synthase to 43% had no effect on the growth rate, showing that the capacity of CTP synthase in the cell is in excess in a wild-type strain. ...

8p dell39 03-04-2013 44 5   Download

CCR5 is a G protein-coupled receptor that binds several natural chemokines but it is alsoa coreceptor for the entryof M tropic strains of HIV-1 into cells. Levels of CCR5 on the cell surface are important for the rate ofHIV-1 infectionand are determined by a number of factors including the rates of CCR5 internalization and recycling. Here we investigated the involvement of the actin cytoskeleton in the control of ligand-induced internalization and recycling of CCR5.

10p dell39 03-04-2013 45 3   Download

This work investigated the kinetics of catabolism and the catabolic fate of the newly synthesized 35 S-labelled proteo-glycans present in explant cultures of tendon. Tissue from the proximal region of bovine deep flexor tendon was incu-bated with [ 35 S]sulfate for 6 h and then placed in explant cultures for periods of up to 15 days. The amount of radi-olabel associatedwithproteoglycans and free [ 35 S]sulfate lost to themediumand retained in thematrixwas determined for each day in culture.

9p dell39 03-04-2013 22 3   Download

When molecules are present in small numbers, such as is frequently the case in cells, the usual assumptions leading to differential rate equations are invalid and it is necessary to use a stochastic description which takes into account the randomness of reactive encounters in solution.

12p dell39 27-03-2013 33 2   Download