Samples cuvettes

To construct a standard curve of various biotin concentrations, first zero a spectrophotometer at an absorbance setting of 500 nm with sample and reference cuvettes filled with 0.05M sodium phosphate, 0.15M NaCl, pH 6.0. Remove the buffer solution from the sample cuvette and add 3 ml of the (strept)avidin solution plus 75 pi of the HABA-dye solution. Mix well and measure the absorbance of the solution at 500nm. Next add 2 pi aliquots of the biotin solution to this (strept)avidin-HABA solution, mix well after each addition, and measure and record the resultant absorbance change at 500 nm. With each addition of biotin, the absorbance of the (strept)avidin-HABA complex at 500 nm decreases. The absorbance readings are plotted against the amount of biotin added to construct the standard curve. 

In situations where absorption of the incident radiation by the transducing gas is troublesome a piezoelectric transducer (made from barium titanate, for example) can be attached to the sample (or sample cuvette in the case of liquids) to detect the thermal wave generated in the sample by the modulated light (8,9). The low frequency, critically damped thermal wave bends the sample and transducer thus producing the piezoelectric response. The piezoelectric transducer will also respond to a sound wave in the solid or liquid but only efficiently at a resonant frequency of the transducer typically of the order of 10 to 100 KHz (see Figure 4). Thus neither in the case of microphonic nor piezoelectric detection is the PA effect strictly an acoustic phenomenon but rather a thermal diffusion phenomenon, and the term "photoacoustic" is a now well established misnomer. 

Since the sample cuvette is the flame located in an open area of the atomic absorption instrument, rather than a glass container held in the light tight box in the case of molecular instruments, how is room light prevented from reaching the detector and causing an interference ... 

Figure 6.14. Kinetics of 02 secretion by activated neutrophils. Neutrophil suspensions (5 x 10s/ml) were suspended in RPMI 1640 medium containing 75 /JM cytochrome c. In (b) and (d), suspensions contained 100 nM staurosporine. At time zero, suspensions in (a) and (b) were stimulated by the addition of 1 /iM fMet-Leu-Phe, whilst suspensions in (c) and (d) were stimulated by the addition of 0.1 fi g/ml PM A. Reference cuvettes were identical to the sample cuvettes, but additionally contained 30 jUg/ml SOD. The bar marker represents a A4 of 0.03 in (a) and (b), or 0.08 in (c) and (d). Similar results were obtained using the more specific protein kinase C inhibitor, bisindolylmaleimide.

As shown in Figure B2.1, double-beam spectrophotometers automatically record the true absorbance by measuring log(IR/Is), thanks to a double compartment containing two cuvettes, one filled with the solution and one filled with the solvent. Because the two cuvettes are never perfectly identical, the baseline of the instrument is first recorded (with both cuvettes filled with the solvent) and stored. Then, the solvent of the sample cuvette is replaced by the solution, and the true absorption spectrum is recorded. 

The solubility was determined spectrophotometrically on a Shimadzu UV160A using the reference quartz cuvette filled with pure vegetable oil under testing and the sample cuvette filled with the solution of C60 or C70 in a given vegetable oil. 

A) Hepatic microsomes from female rats pretreated with 3-methylcholanthrene (20 mg/kg, for 4 days) were divided between 2 cuvettes and a baseline of equal light absorbance obtained. A few mg of Na2S20/f were added to the reference and sample cuvettes and ethylisocyanide (final concentration about lOmM) was added to the sample cuvette. The difference spectrum between 390 and 500 nm was then recorded (protein concentration, 0.75 mg/mL total P-450 concentration 0.85 /xM). (B) Conditions as in (A), but control hepatic microsomes were used. (Protein concentration, 0.72 mg/mL total P-450 concentration, 0.41 M). 

Hydroperoxides may be determined by measuring at 290 nm (e = 44100 M cm ) or 360 nm (e = 28000 cm ) the concentration of 13 formed in the presence of a large excess of ions. The reaction may be too slow for practical purposes, unless a catalyst is present. For example, an assay for lipid hydroperoxides conducted without a catalyst may require several measurements every 6 min until the absorbance reaches a maximum. Exclusion of air from the sample cuvette is important. The method is about 1000-fold more sensitive than thiosulfate titration The iodometric method with UVD at 360 was adopted for detecting the presence of hydroperoxides derived from protein, peptide or amino acid substrates subjected to y-radiation, after destroying the generated H2O2 with catalase. ... 

T at 540 nm read from sample cuvette containing color developed solution. % T displayed in digital format. 

Sample cuvette with c moles/liter of absorbing species... 

Sample chambers for spectrometers come in two varieties—those holding only one cuvette at a time (single-beam) and those holding two cuvettes, one for a reference, usually solvent, and one for sample (double-beam). In a double-beam instrument, the sample spectrum is continuously corrected by subtraction of the reference spectrum. In the past, single-beam instruments were usually less expensive but more cumbersome to use because reference and sample cuvettes required constant exchange. However, modern singlebeam instruments with computer control and analysis can be programmed to correct automatically for the reference spectrum, which may be stored in a memory file. The use of both types of instruments is outlined in the applications section. 

To zero the spectrophotometer, successively pipet 950 pi assay buffer, 40 pi of 12.5 mM substrate solution, and 10 pi of the buffer in which the enzyme is dissolved into reference and sample cuvettes (total 1 ml each cuvette). Place in the cuvette holders and zero the instrument. 

Discard the contents of the sample cuvette and leave the reference cuvette in place. 

Fig. 7. TL spectrometer C, sample cuvette PH, pinhole F, filter BS, beam splitter PD, pyroelectric detector D, diode P 90° prism L, lens...

Figure 3 MIC formation by diltiazem (5 pM) in HLMs. The sample cuvette contained HLMs, diltiazem, and NADPH, whereas the reference cuvette contained HLMs, buffer, and NADPH. The ribbons represent the change in absorbance difference for scans from 5 to 120 minutes. Abbreviations MIC, metabolic intermediate complex HLMs, human liver microsomes. Source From Ref. 37.

To the sample cuvette, add with a pipette Pasteur very small quantity of Calcofluor White powder, then mix slowly. 

Dissolve in the new sample cuvette small quantity of lyophilized a i -acid glycoprotein. Plot protein absorption spectrum from 200 to 400 nm. 

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