Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spectrophotometry”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed1980

Determination of zinc in diet and faeces by acid extraction and atomic absorption spectrophotometry.

A simple acid extraction procedure for sample preparation of diet and faeces for zinc analysis by flame atomic absorption spectrophotometry is evaluated. About 0.5 g of homogenized diet or faeces was mixed with 6 ml 1 mol/l hydrochloric acid. After 24 h, 4 ml chloroform and 2 ml methanol was added to dissolve fatty components and reduce surface tension. The samples were centrifuged and the supernatants analysed. The sensitivity of the method was 1.7 mumol per 1000 g. The coefficient of intra-assay variation was for faeces 1.7% (n = 20), for diet 2.1% (n = 25). The coefficient of inter-assay variation was for faeces 4.7% (n = 24), for diet 4.9% (n = 20). Recovery of known amounts of zinc added to faeces was 99.7 +/- 3.1% (n = 50). Recovery of zinc added to diet was 98.9 +/- 2.9% (n = 47). A good agreement was found between zinc determinations by the acid extraction method and by a method of acid digestion.

Analysis of Variance↗
PubMed1980

Determination of inorganic plasma sulfate by indirect atomic absorption spectrophotometry.

An indirect method for the determination of inorganic sulfate in small plasma volumes is presented. After removal of protein and phosphate by uranylacetate, sulfate is precipitated by barium chloride. Excess barium in the supernatant is measured by atomic absorption spectrophotometry. The sulfate content of the sample corresponds to the difference of the added and the measured barium. The mean concentration of inorganic plasma sulfate of healthy children, determined by this method, was 0.241 +/- 0.059 mmol/l.

Adolescent↗
PubMed1982

Method for the simultaneous determination of cadmium and zinc in whole blood by atomic absorption spectrophotometry and measurement in normotensive and hypertensive humans.

A method is described for the analysis of whole blood cadmium and zinc by extraction and atomic absorption spectrophotometry, in which cadmium is analyzed using a graphite furnace, and zinc using an air-acetylene flame with a single slot burner, after dilution of the extract. Recoveries for cadmium and zinc were 100% and 106%, respectively. For cadmium the day-to-day and within-run coefficients of variation were all less than 13% at low concentrations (approximately 27 nmol/1) and 6% or less at high concentrations (approximately 89 nmol/1). For zinc the coefficients of variation for day-to-day and within-run analyses were less than 6% at low (approximately 76 mumol/1) and high concentrations (approximately 138 mumol/1). The sensitivity of the procedure is 0.5 nmol/1 for cadmium and 1.2 mu mol/1 for zinc. Whole blood from 72 normotensive volunteers, 56 treated hypertensives, and 15 untreated hypertensives were analyzed using this method. Cadmium levels were elevated in smokers but not significantly affected by age or sex. Zinc levels were higher in males than in females, but not significantly affected by smoking. Levels of cadmium and zinc were increased in treated hypertensives and greater still in untreated hypertensives. Significant elevations were found for cadmium in treated hypertensive females who smoked, treated and untreated hypertensive male non-smokers, and for the cadmium to zinc ratio in these later two groups.

Cadmium↗
PubMed1985

Semi-automated determination of chromium in whole blood and serum by Zeeman electrothermal atomic absorption spectrophotometry.

Direct determination of normal and elevated levels of chromium in whole blood and serum can be achieved using Zeeman effect electrothermal atomic absorption spectrophotometry. Whole blood and serum levels of chromium were determined for an apparently healthy population and whole blood chromium levels for renal dialysis patients. Blood and serum specimens were diluted with distilled deionized water and Triton X-100. The analyses were performed utilizing air as the alternate gas to facilitate ashing in one of the char steps. Within-run precision studies for whole blood chromium determinations gave relative SD values of 4.75 and 4.65% for 0.358 and 0.172 microgram/l, respectively. Within-run precision studies for the serum chromium analysis yield relative SD values of 5.26 and 2.67% for 0.156 and 0.300 microgram/l, respectively. Detection limits were 0.025 and 0.018 microgram/l for whole blood and serum, respectively. The mean chromium level found in whole blood and serum specimens from apparently normal individuals were 0.371 microgram/l (n = 37) and 0.130 microgram/l (n = 19), with ranges of 0.120-0.673 and 0.058-0.388 microgram/l, respectively.

Autoanalysis↗
PubMed1989

Simultaneous determination of hemoglobin and coproporphyrin by second derivative differential spectrophotometry: application to the diagnosis of meconium aspiration.

We describe a simple, fast method for simultaneous measurement of hemoglobin and coproporphyrin in urine and amniotic fluid, by second-derivative differential spectrophotometry. Both pigments were determined in biological samples without prior extraction. Despite the slightly overlapping spectra, the method permitted satisfactory resolution and avoided interspectral interference. Its sensitivity, sufficiently good, allowed to detect hemoglobin and coproporphyrin in slightly pathological urine and amniotic fluid as an aid to the diagnosis of meconium aspiration.

Amniotic Fluid↗
PubMed1985

Bacterial immunoglobulin A proteases monitored by continuous spectrophotometry.

IgA proteases were estimated in a turbid aqueous two-phase system with 10% polyethylene glycol-Tris buffer, where IgA spontaneously concentrates in microscopic spherical particles (less than 1 micron). After enzymatic cleavage of IgA into Fab alpha and Fc alpha fragments, these fragments are soluble and decreasing turbidity is observed. The reaction may be followed by conventional spectrophotometry. In this manner, IgA proteases may be estimated in 10 min. Examples of the utility of the method are given with results from inhibitor studies, estimation of Km and purification of IgA protease from Haemophilus influenzae.

Autoanalysis↗
PubMed1988

Concurrent assessment of inner and outer membrane permeabilization and bacteriolysis in E. coli by multiple-wavelength spectrophotometry.

We developed a dual wavelength spectrophotometric assay that permitted beta-lactamase and beta-galactosidase activities to be measured concurrently in a single sample. We also constructed a target cell, E. coli ML-35p, that was substantially cryptic for its periplasmic beta-lactamase and cytoplasmic beta-galactosidase unless outer membrane (beta-lactamase) or inner membrane (beta-galactosidase) permeabilization occurred. By applying the spectrophotometric assay to whole target cells, we could ascertain the kinetics of inner and outer membrane permeabilization by biological agents, including serum, polymyxin B and mellitin. By monitoring the reactions at an additional wavelength, we could also follow the kinetics of serum-mediated bacteriolysis. These experiments illustrate the principle of multiple wavelength spectrophotometry and provide examples of its use to monitor and dissect the action of biological agents on a gram-negative bacterium.

Bacteriolysis↗
PubMed1975

Cerebral haemorrhages with atypical clinical patterns. A study of cerebral haematomasusing CSF spectrophotometry and computerized transverse axial tomography ("EMI scanning").

Twelve patients with 13 cerebrovascular incidents presenting with atypical clincial patterns where thecombination of CSF spectrophotometry (CSF-SPE) and computerized transverse axialtomogrpahy(CTAT, "EMI-scanning") showed cerebral haematomas, with or without haemorrhage into the CSFare reported. The high diagnostic significance of SDF-SPE as well as the value of using a combination of CSF-SPE and CTAT examinations in cerebrovascular disease has preveiouslybeen established by the authors. The present patient group comprised some 10% of a totalseries of patients with cerebrovascular disease hitherto studied in this fashion. Conclusive findings were found in only 1 fo the 5 cases examined by angiography and in none of the5 cases studied by isotope scan. Since many cerebral haemorrhages obviosly haveatypical clincalfeatures as compared with the "classical" pattern, the combined use of CSF-SPE and CTAT examinations in the diagnosis of cerebral haematomas is a prereguisite for rational therapy.

Adult↗
PubMed1978

Spectrophotometry of the CSF (CSF-SPE) and computer tomography (CT) in traumatic head injuries.

Combined examinations with quantitative CSF spectrophotometry (CSF-SPE) and computer tomography (CT) were performed on 53 patients with traumatic head injuries. In cerebral concussion the results were mainly normal in both examinations. In cerebral contusion bleeding patterns were found by CSF-SPE in all subjects, with a special bleeding pattern (S2 pattern) occurring in 86%. CT showed findings described as typical for contusion in 8 of 14 examined patients, the remaining CT scans showing questionable or normal signs. In extra- and intracerebral haematomas, all patients had bleeding patterns on the CSF-SPE. A special bleeding component (H factor) was found in about 72%. The H component was not observed during the first 3 to 4 days after the trauma. All but one patient examined later than the 4th day had an H component with or without an S-pattern. CT demonstrated a haematoma in 14 of 18 verified haematoma patients, while 4 subjects with subdural haematoma (e.g. one third of this group) had questionable CT findings. The combined examinations with CT and CSF-SPE, being complementary to each other, are of great value in the different diagnosis of traumatic head injuries.

Brain Concussion↗
PubMed1995

Spectrophotometry of amniotic fluid: a simple and rapid method for distinguishing between gestational sacs in second-trimester amniocentesis of twin pregnancies.

OBJECTIVE: To evaluate the use of an alternative and simple spectrophotometric method that could replace the intraamniotic injection of dye in the second-trimester amniocentesis of twins. METHODS: Optical densities (OD) of amniotic fluid (AF) obtained at second-trimester genetic amniocentesis were measured at 360 nm. Comparison was made between 36 twin pregnancies and 60 singleton controls. RESULTS: The mean difference in OD between two samples taken from the same sac of singleton pregnancies was very small (mean 0.004, standard deviation [SD] 0.003). However, samples drawn from each of the twin pairs' amniotic sacs varied widely (raw mean 0.176, SD 0.223; median 0.096, range 0.011-0.943). The difference between the groups was highly significant statistically (P < .001). CONCLUSION: Our preliminary experience with spectrophotometry of AF in twin amniocentesis suggests that this simple test may be useful in ascertaining that the AF samples were obtained from each of the two gestational sacs.

Amniocentesis↗
PubMed1984

Primary intermediates of rhodopsin studied by low temperature spectrophotometry and laser photolysis. Bathorhodopsin, hypsorhodopsin and photorhodopsin.

The primary photochemical processes of rhodopsin studied by low temperature spectrophotometry and picosecond laser spectroscopy in our group was summarized. Low temperature spectroscopic experiments demonstrated that the retinylidene chromophores of hypso- and bathorhodopsins are in a twisted all-trans forms. Excitation of rhodopsin with 532 nm laser pulse (width: 25 psec) yielded a new bathochromic photoproduct "photorhodopsin"; its spectrum was located at longer wavelengths than that of bathorhodopsin. Photorhodopsin decays to bathorhodopsin with time constants of about 200 psec in squid and 40 psec in cattle. Squid and octopus hypsorhodopsins were produced within 25 psec by high energy pulse, but not by low energy pulse. Thus hypsorhodopsin is produced by two photon reactions (sequential two photochemical reactions) and decayed to bathorhodopsin with time constant of 125 psec.

Animals↗
PubMed1989

Quality control procedures for monitoring whole blood and plasma trace metal levels by atomic absorption spectrophotometry.

Well co-ordinated quality control procedures are required to insure that trace metal results determined at ppb (micrograms kg-1 or micrograms l-1) levels by atomic absorption spectrophotometry are reliable. Control materials can be prepared "in-house" provided they are calibrated against standard reference materials (SRM). A mean +/- SD data base should be determined for each quality control material with daily results plotted on Levey-Jennings charts. Westgard's multi-rule quality control scheme is recommended for assessing analytical performance. Additional information may be obtained by using cumulative sum (cusum) charts to detect analytical drift from the mean, and standard deviation index or 'z-score' plot to show analytical bias. Proficiency or quality assurance programs should be used to supplement internal quality verification of analytical performance.

Humans↗
PubMed1994

Determination of tin in biological materials by atomic absorption spectrophotometry and neutron activation analysis.

Concentrations of Tin (Sn) were determined in botanical, dietary and biological reference materials (RMs), and in human livers from Japanese and American subjects using atomic absorption spectrophotometry (AAS) and neutron activation analysis (NAA), either in the instrumental mode (INAA) or in the radiochemical mode (RNAA). The mean Sn concentrations (+/- 1 S.D.) found in various RMs are: total diet (NIST SRM-1548) 3.57 +/- 0.52 and 3.61 +/- 0.52 microgram/g by AAS and INAA, respectively; non-fat milk powder (NIST SRM-1549) 2.5 +/- 1.4 ng/g and 1.9 +/- 0.3 ng/g; bovine liver (NBS SRM-1577) 18 +/- 2 and 20 +/- 0.3 ng/g; and citrus leaves (NIST SRM-1542) 0.25 +/- 0.02 and 0.243 +/- 0.006 microgram/g by AAS and RNAA, respectively. These comparisons demonstrate good agreement between the two methods. In apple leaves (NIST SRM-1515) and peach leaves (NIST SRM-1547), the measured concentrations by AAS were 77.1 +/- 20 and 85 +/- 15 ng/g; interferences by 160Tb did not permit an accurate assessment by INAA at this concentration. The Sn results obtained for the American human liver specimens by RNAA ranged from 0.135-0.712 microgram/g wet weight, and the Sn concentrations in Japanese human liver specimens determined by AAS ranged from 0.078-1.122 microgram/g wet weight in 23 individuals. The results from this study show that it is feasible to use INAA/RNAA and AAS in combination to establish recommended values in RMs.

Animals↗
PubMed1984

Studies of copper(II) binding to glycylglycyl-L-tyrosine-N-methyl amide, a peptide mimicking the NH2-terminal copper(II)-binding site of dog serum albumin by analytical potentiometry, spectrophotometry, CD, and NMR spectroscopy.

Unlike human serum albumin (HSA), dog serum albumin (DSA) does not possess the characteristics of the specific first binding site for Cu(II). In DSA, the important histidine residue in the third position, responsible for the Cu(II)-binding specificity in HSA, is replaced by a tyrosine residue. In order to study the influence of the tyrosine residue in the third position of DSA, a simple model of the NH2-terminal native sequence tripeptide of DSA, glycylglycyl-L-tyrosine-N-methylamide (GGTNMA) was synthesized and its Cu(II)-binding properties studied by analytical potentiometry, spectrophotometry, CD, and NMR spectroscopy. The species analysis indicated the existence of five mono-complexes at different protonation states: MHA, MA, MH-1A, MH-2A, MH-3A, and only one bis-complex MH-2A-2. The complexing ability of GGTNMA to Cu(II) was found to be weaker than that of the Cu(II) binding peptide models of HSA. The visible absorption spectra of Cu(II)-GGTNMA complexes are similar to those observed in the case of DSA-Cu(II) complexes. The weaker binding and the spectral properties of Cu(II)-GGTNMA complexes are consistent with less specific Cu(II)-binding properties of the peptide of this sequence similar to what was noted with DSA. CD results are in excellent agreement with species analysis and visible spectra where it is clearly evident that Cu(II) binds to GGTNMA starting from the alpha-NH2 group and step by step to deprotonated amide nitrogens as the pH is raised. The absence of any charge transfer band around 400 nm strongly indicates that Cu(II) does not bind to the phenolate group. Furthermore, NMR results are consistent with the noninvolvement of the tyrosine residue of GGTNMA in Cu(II) complexation. Thus, it is clear that the low Cu(II)-binding affinity of DSA is due to the genetic substitution of tyrosine for histidine at the NH2-terminal region of the protein.

Animals↗
PubMed1993

The binding of Yb(III) and Gd(III) to bovin serum albumin by a competitive spectrophotometry.

A competitive spectrophotometry has been used to study the binding of Yb(III) and Gd(III) to BSA. The indicator ligand, 5-Br-PAPS, as well as its metal complexes, ML, having intense colors with sufficiently separate absorption peaks permits the analysis of the interaction between metal and BSA. Experimental data are analyzed by using Scatchard plots. The results show that both Yb and Gd bind to BSA with four equivalent affinity sites at pH 6-7. Some additional lower affinity sites are observed for Gd but not for Yb. The slope of the plots, the apparent association constant of the metal with BSA, decreases with decreasing pH. The pH dependence of the apparent association constant indicates the 1:1 competition between metal ions and hydrogen ions for the binding site. The intrinsic association constant of the metal, KM(H-1A), and the proton association constant, KH(H-1A) =, are found to be logKM(H-1A) = 7.00 +/- 0.03 and log KH(H-1A) = 7.08 +/- 0.06 for the Yb binding sites, and logKM (H-1A) = 6.16 +/- 0.08 and log KH(H-1A) = 6.63 +/- 0.10 for the Gd binding sites by a graphical analysis (A = BSA).

Binding Sites↗
PubMed1987

Quantitative measurement of cerebral cytochrome P-450 by second derivative spectrophotometry.

Second order derivative spectrophotometry was used to improve the accuracy and reproducibility of cytochrome P-450 measurements in subcellular fractions obtained from the brain. This method allowed better resolution of the overlapping bands of cytochrome P-450 and other iron proteins, as well as a reduction of the effects of turbidity and non-specific components. Using this method, the cytochrome P-450 content of rat brain mitochondrial and microsomal fractions was measured to be 74.2 +/- 2.3 and 5.9 +/- 0.3 pmol/mg protein, respectively.

Animals↗
PubMed1993

Use of laser flash photolysis time-resolved spectrophotometry to investigate interprotein and intraprotein electron transfer mechanisms.

A description is given of the methodology developed in our laboratory for the application of laser flash photolysis to the elucidation of the kinetics and mechanism of electron transfer processes which occur intermolecularly between two protein molecules within a collisional complex, or intramolecularly between two redox centers within a single multisubunit or multidomain protein. This involves the use of flavin analogs, excited to their lowest triplet state by a laser flash, to initiate electron transfer, either by oxidation of a sacrificial donor followed by redox protein reduction via the flavin semiquinone, or by direct oxidation of a reduced redox protein by the flavin triplet. Time-resolved spectrophotometry is used to follow the course of the sequence of electron transfer events initiated by the laser flash. The application of this methodology to the following systems is described: cytochrome c/cytochrome c peroxidase; ferredoxin/ferredoxin NADP+ reductase; cytochrome c/plastocyanin; flavocytochrome b2; and sulfite oxidase.

Animals↗
PubMed1992

Decay kinetics of O2.- studied by direct spectrophotometry. Interaction with catalytic and non-catalytic substances.

The kinetic behaviour of O2.- during spontaneous dismutation and in the presence of Cu,Zn-superoxide dismutase and other compounds, was studied by monitoring the decrease in absorbance (A250nm-A360nm) on a time-scale of > or = 1 min, at pH 9.5. O2.- was generated from KO2, and calculations were performed between 25 and 4 microM of O2.-. An algorithm for the simultaneous calculation of the 1st and 2nd-order rate constants from the decay curve, was evolved. The respective fractions of O2.- which interacted with catalysts or disappeared spontaneously, in various experimental situations, could be estimated. Substances could be classified as inert, catalysts or scavengers. The high assay pH excluded examination of the effect of alkali sensitive substances, e.g., Mn-superoxide dismutase. However, the high pH minimized the interfering effect of trace amounts of Cu(II). Therefore a metal chelator was superfluous and even the effect of metals and metal complexes could be tested. The extremely high sensitivity of the method allowed minute concentrations of reagents to be used, including proteins absorbing in the UV-region. The rate constants found by this simple method, agreed with those obtained by more sophisticated and inaccessible techniques like pulse radiolysis and stopped-flow spectrophotometry.

Hydrogen-Ion Concentration↗