Assays colorimetric

The most widely appHed colorimetric assay for amino acids rehes upon ninhydrin-mediated color formation (129). Fluorescamine [38183-12-9] and (9-phthalaldehyde [643-79-8] are popular as fluorescence reagents. The latter reagent, ia conjunction with 2-mercaptoethanol, is most often used ia post-column detection of amino acids separated by conventional automated amino acid analysis. More recently, determiaation by capillary 2one electrophoresis has been developed and it is possible to determine attomole quantities of amino acids (130). 

Other specific discovery assays have been used such as differential inhibition of a vancomycin resistant S. aureus strain and its susceptible parent, and an assay based on antagonism of the antibacterial activity by N,A/-diacetyl-L-Lys-D-Ala-D-Ala [24570-39-6] a tripeptide analogue of the dalbaheptides receptor. AppHcation of this latter test to 1936 cultures (90) led to the isolation of 42 dalbaheptides, six of which, including kibdelin (Table 3), parvodicin (Table 3), and actinoidin A2 (68) were novel. A colorimetric assay based on competition between horseradish peroxidase bound teicoplanin and the... 

The AO AC (978.42) recognizes a similar procedure, except that the unsap onitiable material is treated with maleic anhydride to remove the trans-isomer which may possibly be present (83). The antimony trichloride colorimetric assay is performed on the trans-isomer-free material. This procedure cannot be used to distinguish certain inactive isomers, eg, isotachysterol if present, these are included in the result, giving rise to a falsely high analysis. A test must therefore be performed to check for the presence of isotachysterol. 

The reaction between 6-aminopenicillanic acid (6.5 g) and 3-o-chlorophenyl-5-methyllsoxa2ole-4-carbonyl chloride (7.66 g) gave the sodium salt of 3-o-chlorophenyl-5-methyl4-isoxa2olyl-penicillin (9.9Bg) asa pale yellow solid. Colorimetric assay with hydroxy lamina against a ben2-ylpenicillin standard indicated a purity of 6B%. 

Crystallization was initiated, and completed at about 0°C overnight, to give the sodium salt of Q-(benzyloxycarbonyl)-3-thienylmethylpenicillin as white crystals in 50% weight yield. This product was estimated by colorimetric assay with hydroxylamine to contain 91% of the anhydrous sodium salt. 

Colorimetric assay with hydroxylamine showed this salt to contain 94% of the anhydrous penicillin. Paper chromatography showed complete reduction of the benzyl group. 

The use of HPLC for quantification of phenols is often limited to a single class of phenolics and then often only to low-molecular weight compounds that are available as standards. It is, therefore, often necessary to use colorimetric assays such as the Folin-Ciocalteau assay which rely on the reducing ability of phenols to quantify the amount of total phenolics in a sample (Waterman and Mole, 1994 Singleton et al, 1999 Schofield et al, 2001). The degree of condensation of polyphenols can be quantified by colorimetric assays such as the acid-butanol assay and the vanillin assay (Waterman and Mole, 1994 Schofield et al, 2001). 

Tomato fruits (Lycopersicon esculentum Mill. var. Castlemart ) were collected from vines grown in the field at the University of California, Davis. Pericarp discs were cut from surface sterilized MG stage fruit (10). Droplets (10 n ) of test solutions (see below) were applied to the cut surface of discs and disc ethylene production was measured as described previously (11). The amounts of test materials used were based on colorimetric assay (6) of uronic acid content. 

Table II. Carbohydrate compositions (weight percentage) of individual oligomer peaks purified (QAE-Sephadex or HPLC ion-exchange separation, respectively) from mixtures of citrus pectin oligomers or B fruit extracts Compositions shown are for peaks whose biological activity is described in Figure 4. Uronic acid values are based on colorimetric assay. Proportions of neutral sugars were determined by GC and adjusted so that totals equal 100%. In fact, some oligomers (G7 peaks 8, 9 and 10. B extract peak 10) produced small (less than 1 % of the total integrated area), unknown peaks in the GC chromatograms.

A further partihon system based on the use of liposomes, and commercialized under the name Transil [110, 111], has shown its utiUty as a UpophiUcity measure in PBPK modeling [112]. Fluorescent-labeled liposomes, called fluorosomes, are another means of measuring the rate of penetration of small molecules into membrane bilayers [113, 120]. Similarly, a colorimetric assay amenable to HTS for evaluating membrane interactions and penetrahon has been presented [116]. The platform comprises vesicles of phospholipids and the chromahc Upid-mimehc polydiacetylene. The polymer undergoes visible concentrahon-dependent red-blue transformahons induced through interactions of the vesicles with the studied molecules. 

The diabetic rats were treated with 18 IU of bovine insulin imbibed into polyacid resins b.i.d. orally using 1 cc syringes and gavage tubes. After 14 days of treatment the rats were sacrificed about 1.5 hours after the last dose. Blood samples were taken and assayed for immunoactive insulin activity (Amersham-Searie RIA kit) and serum glucose levels (glucose oxidase colorimetric assay, Sigma 510 Glucose Kit). 

Denizot F, Lang R 1986 Rapid colorimetric assay for cell growth and survival. Modifications to the tetrazolium dye procedure giving improved sensitivity and reliability. J Immunol... 

Figure 15.8 (a) Time course of the activity restoration of formalin-treated RNase A during incubation at 50°C (0-2h) and 65°C (2-4h) in TAE buffer, pH 7.0. (b) Time course of the activity restoration of formalin-treated RNase A during incubation at 65°C in TAE buffers of various pH values. All RNase A preparations were freed of excess formaldehyde by dialysis prior to the assay. The RNase A activity was determined with a colorimetric assay using cytidine 2,3,-cyclophosphate as the substrate as described by Crook et al.54 Note that the slopes of the curves decrease with incubation time at 65°C, which is near the denaturation temperature of native RNase A. This loss of activity is likely due to the competing effect of protein denaturation of the recovered RNaseA at this temperature. See Rait et al.10 for details. 

Lee, K.Y., Birckbichler, P.J., and Patterson Jr., M.K. (1988) Colorimetric assay of blood coagulation factor XIII in plasma. Clin. Chem. 34, 906-910. 

Total flavonoid content. Quantitative analysis of flavonoids depends on the objective of the study. Colorimetric estimation of total flavonoid content is measured by the aluminum chloride colorimetric assay (Jia and others 1999 Chang and others 2002). The total flavonoid content measured in this way is normally expressed in equivalent values of a standard flavonoid, often catechin or quercetin equivalents. Not all subgroups of flavonoids can be quantified by colorimetric methods however, total anthocyanin content is determined using the pH-differentiation method (Boyles and others 1993). 

Lussignoli S, Fraccaroli M, Andrioli G, Brocco G and Bellavite P. 1999. A microplate-based colorimetric assay of the total peroxyl radical trapping capability of human plasma. Anal Biochem 269(7) 38-44. 

To test our new signal reagent based on GZ-11 the detection system was applied to two competitive-format immunoassays. These two assays (for atrazine and clenbuterol) normally use chromogenic detection systems. While these colorimetric assays may be adequate for laboratory use, chemiluminescent detection offers potential advantages in sensitivity and on site screening applications [33],... 

Rittenberg and coworkers used a colorimetric assay for tryptophane to determine tyrothricin in fermentation broth152. Kreuzig described a semi-automated colorimetric assay for gramicidin utilizing the reaction of... 

A colorimetric assay of griseofulvin, based on the yellow-orange color (Xmax=420 nm) which develops when griseofulvin is heated with isonicotinic acid hydrazide in alkaline medium has been described by Unterman (35) and the mechanism investigated by Unterman and Duca (36). 

An automated colorimetric assay for the quantitation of the separate components of neomycin (B, C and neamine) has also been reported- - . The method utilizes a separation of the components on a column of carbon and Kieslguhr G (4 1). The column eluate is reacted with nin-hydrin to determine the amounts of neomycin B, C and neamine. 

Detergent should be inexpensive Detergent should be easily removable Detergent should not interfere with assays such as lipid and protein colorimetric assays and enzyme assays... 

Morken and co-worker (57) recently reported using a visual colorimetric assay to evaluate a variety of catalyst systems for allylic alkylation. This method uses the reaction of naphthol with Fast Red diazonium salt as a method for determination of catalyst activity. Reaction of the naphthyl allyl carbonate (222) with palladium gives the naphthoxide (223) after loss of C02. The naphthoxide then deprotonates... 

A colorimetric assay for lecithin and choline was described by Kotsira and Klonis (1998) using two enzymes (phospholipase and choline oxidase) and an indicator dye conjugate (bromothymol blue-glutathione) co-immobilised on a glutaraldehyde-activated polyacrylamide transparent gel. The change of the... 

---