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1.
A spectrophotometric assay of β-lactamase action on penicillins (Short Communication) 总被引:42,自引:0,他引:42
Stephen G. Waley 《The Biochemical journal》1974,139(3):789-790
A new method for measuring the enzymic hydrolysis of the beta-lactam ring in penicillins is described. The change in extinction in the u.v. region is determined. The method is sensitive (50mum-benzylpenicillin can be used) and convenient. 相似文献
2.
John L. Wood 《The Biochemical journal》1974,143(3):775-777
The pH-dependence of the degree of hydrogen-bonding between a base and its conjugate acid is considered. When only a small proportion of the total base is complexed, the amount complexed is proportional to (1+coshp)(-1) where p=2.303 (pK(a)-pH), pK(a) being the dissociation constant of the conjugate acid. This represents sharp pH-dependence. As the proportion complexed increases, the curve broadens, eventually becoming flat-topped, with more than half the base complexed over the range of pH values pK(a)+/-logKC, approximately. (K is the complex association constant and C is the formal base concentration, including all forms.) There are similarities to the extent of mono-protonation of a dibasic acid. 相似文献
3.
An improved fluorometric assay for DNA 总被引:110,自引:0,他引:110
R T Hinegardner 《Analytical biochemistry》1971,39(1):197-201
A modification of the fluorometric assay of Kissane and Robins is described. The modified procedure is very accurate, widely applicable, and reasonably easy to use. A standard cell type instead of a standard DNA solution makes the assay universally reproducible. DNA content is calculated by a simple method from the slope of a DNA concentration series. This can be used to detect technique erros. 相似文献
4.
The use of phosphoenolpyruvate plus pyruvate kinase as an ATP-generating system in the assay for glutamine synthetase activity via the formation of gamma-glutamylhydroxamate from glutamate and hydroxylamine with crude tissue preparations is shown to give values far in excess of the true glutamine synthetase activity of the tissue. This is due to the generation of pyruvate, which reacts with hydroxylamine to give a compound that is chromogenic with the ferric chloride reagent used for measuring gamma-glutamylhydroxamate. 相似文献
5.
An improved glucoseoxidase-peroxidase-coupled assay for the determination of β-fructofuranosidase activity is described. The method makes use of the double effect of Tris (2-amino-2-hydroxymethylpropane-1,3-diol) as an inhibitor of both invertase and contaminating glucosidases. The method is very sensitive and is suitable for routine determinations. The total time needed for a single analysis is less than half an hour. 相似文献
6.
An improved assay for long-chain acyl-CoA synthetase 总被引:1,自引:0,他引:1
7.
An improved in vitro assay for lymphotoxin 总被引:7,自引:0,他引:7
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10.
An improved assay for interleukin 2 (lymphocyte growth factor) produced by mitogen-activated lymphocytes 总被引:6,自引:0,他引:6
K J Lafferty S J Prowse A Al-Adra H S Warren J Vasalli E Reich 《The Australian journal of experimental biology and medical science》1980,58(6):533-544
The continued proliferation of activated T cells requires the presence of a lymphocyte growth factor in the culture medium. This study describes a rapid, highly reproducible assay to quantitatively measure levels of this lymphokine. The use of Concanavalin-A blast cells given this assay a high degree of flexibility and convenience. It is shown that the lymphokine measured is interleukin 2. The presence of an inhibitor in the supernatant of mitogen activated lymphocytes and the species specificity of the factor are demonstrated. 相似文献
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12.
Torben K. With 《The Biochemical journal》1974,137(3):596.2-598
T.l.c. of esterified egg-shell porphyrin shows a mixture containing protoporphyrin with admixture of significant amounts of coproporphyrin, pentacarboxylic porphyrin and uroporphyrin and other, unidentified, porphyrins. This points to porphyrin biosynthesis taking place in the oviduct epithelium. 相似文献
13.
Specificity of anti-nucleoside antibodies (Short Communication) 总被引:2,自引:0,他引:2
The method of conjugation of a nucleoside or related compound to a carrier protein may have a significant effect on the specificity of the antibodies elicited. It is demonstrated, by means of the membrane-filtration assay, that anti-isopentenyladenosine antibodies produced by the ;periodate procedure' are much more reactive with the periodate-oxidized form of the nucleoside than with the parent compound. In addition, the simplicity and specificity of the assay used suggests its use as a sensitive radioimmunoassay for this multifunctional nucleoside. 相似文献
14.
Edwin Haslam 《The Biochemical journal》1974,139(1):285-288
The association of some natural and synthetic polyphenols with beta-glucosidase was examined and some observations on the chemical nature of the complex were made. 相似文献
15.
Edward D. T. Atkins Ian A. Nieduszynski Alan A. Horner 《The Biochemical journal》1974,143(1):251-2521
X-ray fibre-diffraction photographs were obtained from oriented films of the sodium salt of macromolecular heparin (molecular weight approx. 106) prepared from rat skin. Two distinct molecular chain conformations corresponding to two different crystal lattices were observed as a function of relative humidity. The first conformation, obtained at 78% relative humidity, has a layer-line spacing of 1.73nm, which can be interpreted as an approximate twofold helix. On increasing the relative humidity to 84% a second phase with a layer-line repeat of 1.65nm is obtained with the reflexions indexing on a triclinic unit cell similar to that obtained previously (Nieduszynski & Atkins, 1973) for pig mucosal heparin. 相似文献
16.
The activity of a number of alcohols was examined as substrates or inhibitors of glycerol kinase (ATP-glycerol phosphotransferase; EC 2.7.1.30) from Candida mycoderma. On the basis of these and other results, a modified model is proposed to account for the substrate specificity of the enzyme. 相似文献
17.
An improved method for the assay of hydroxylysine 总被引:4,自引:0,他引:4
An improved method for specific detection of hydroxylysine is presented. The procedure is based on the capability of 0.0015 m periodic acid and periodates to oxidize hydroxylysine without interference of proline. Glycosylated hydroxylysine can be detected in collagen by oxidation of unglycosylated residues before hydrolysis. 相似文献
18.
Alan B. Stone 《The Biochemical journal》1974,137(1):117-118
Numerous sucrose gradients can be prepared simultaneously by diffusion in horizontal centrifuge tubes. 相似文献
19.
B.D. Hames 《Analytical biochemistry》1976,73(1):215-219
UDP glucose is an important intermediate in numerous metabolic pathways (1). It is therefore not surprising that the enzyme which catalyses its formation, UDP-glucose pyrophosphorylase is ubiquitous (see (2) for references). The reaction catalysed by UDP-glucose pyrophosphorylase is: and the enzyme has been assayed either in the direction of pyrophosphorolysis of the nucleoside diphosphate sugar or in the direction of UDP-glucose formation.Spectrophotometric assays of UDP-glucose pyrophosphorylase in the direction of pyrophosphorolysis are often nonspecific by virtue of the nature of the coupling enzymes (3), whereas similar assays in the direction of UDPG formation may lack the expected stoichiometry of reaction (3,4). Radioisotopic techniques for the assay of UDP-glucose pyrophosphorylase (5,6) are to be preferred to spectrophotometric assays both for their increased sensitivity and specificity. However, these methods depend upon the specific isolation of the radioactive UDP glucose formed, either by a somewhat tedious adsorption to and elution from charcoal (5) or a hazardous precipitation using mercuric acetate. For routine assay of a large number of samples it would be advantageous to replace these techniques with one involving a safer, more rapid method of radioactive UDP-glucose isolation. The radiochemical assay described in this note utilises the binding of UDP glucose to commercially available, anion-exchange filter-paper discs for this purpose. Although the technique was designed to assay UDP-glucose pyrophosphorylase in cell extracts of the cellular slime mould, Dictyostelium discoideum, it should be applicable to most sources of the enzyme. 相似文献
20.
An improved resazurin-based cytotoxicity assay for hepatic cells 总被引:2,自引:0,他引:2
McMillian MK Li L Parker JB Patel L Zhong Z Gunnett JW Powers WJ Johnson MD 《Cell biology and toxicology》2002,18(3):157-173
A simple resazurin-based cytotoxicity assay is presented for screening of cytotoxicity in hepatocytes and liver cell lines.
Human hepatoma (HepG2) cells in 96-well culture plates were exposed to known toxic (cisplatin, 5-fluorouracil, ethionine,
flufenamic acid, and diflunisal) and control (transplatin, 5-chlorouracil, methionine, and acetylsalicylic acid) compounds
for 1–3 days, and resazurin (5 μmol/L) was added. A conventional short-term (1 h) assay was first performed, where cytotoxicity
is indicated by decreased reduction of resazurin to its fluorescent product resorufin. Our improved assay consists of additionally
measuring fluorescence 2–4 days later, when cytotoxicity is indicated by a striking increase in the concentration of resorufin, resulting from two distinct processes. First, viable liver-derived cells slowly convert
resorufin to nonfluorescent metabolites. Fluorescence of control cell wells decreased to background during a 2- to 4-day exposure
to resazurin. This metabolism of resorufin was largely blocked by dicumarol and to lesser extents by disulfiram and SKF525a.
Second, dead or dying cells slowly convert resazurin to resorufin but do not further metabolize resorufin; thus this fluorescent
metabolite accumulates to high levels in wells with dead cells by 2 to 4 days. A similar increase in fluorescence associated
with cytotoxicity was observed in primary cultures of rat hepatocytes using the long-term resazurin-based assay. In addition
to an improved signal relative to the short-term assay, the inversion of the fluorescent signal from high = alive short-term
to high = dead long-term allows determination of two independent cytotoxicity endpoints after addition of one innocuous vital
dye.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献