Dual wavelength/split beam spectrophotometry: computer acquisition of absorbance spectra.

The adaptation of a commercially available dual wavelength/split beam spectrophotometer for the real time acquisition by a minicomputer of absorbance spectra is described. The computer software and interface are designed so that: a) The normal operation of the spectrophotometer is unaltered; b) the adaptation of the spectrophotometer for computer acquisition of spectra is relatively simple and only a rudimentary knowledge of electronics and computer programming is required.The utility of this adaptation of a dual wavelength/split beam spectrophotometer for baseline correction, enhancement of the sensitivity of the spectrophotometer and subsequent analysis of recorded absorbance spectra is described.     

Use of a Fiber Optic Probe for Spectral Measurements and the Continuous Recording of the Turbidity of Growing Microbial Cultures

This paper describes the properties and use of a fiber optic probe as an attachment to a spectrophotometer and its use for measurements in solutions and turbid suspensions. Measurements of a standard were identical when a spectrophotometer equipped with the probe was used or when a spectrophotometer was used in a conventional manner. The probe was calibrated for turbidimetric measurements with microorganisms by relating the apparent absorbancy measured on the spectrophotometer to the dry weight of each species of organism. Continuous measurements were made of the turbidity of growing cultures of Escherichia coli, Streptococcus mutans, and Saccharomyces cerevisiae. Transient changes in cell mass were observed in some cultures during continuous monitoring of growth. The data were recovered in a manner which allowed direct computer processing.     

黔西北两铜矿4种藓类植物重金属元素分析

坝口铜矿和长箐沟铜矿是峨眉山玄武岩型铜矿。利用3种光谱仪对卷叶丛本藓（Anoectangium thomso-niiMitt.）、酸土藓[Oxystegus cylindricus（Brid.）Hilp.]、硬叶扭口藓[Barbula rigidula（Hedw.）Mild.]和齿边异齿藓[Regmatodon serrulatus（Dozy et Molk.）Bosch et Lac.]及其基质中的Cu、Zn、Ca、Mg、Cd、Pb、Hg和As8种元素进行测定及分析,并计算出富集系数。结果表明,两铜矿Cu、Zn、Cd和Hg的背景值均超标,特别是Hg和Cu的平均含量分别是其标准值的10.28倍和2.33倍。长箐沟铜矿受Hg污染较重,坝口铜矿比长箐沟铜矿含Cu高。Cu-Cd、Zn-Ca、Ca-Pb和Hg-As均在0.05水平显著相关,Zn-Pb在0.01水平显著相关。Cu-Cd、Zn-Pb和Hg-As均产生协同效应。Zn-Ca和Ca-Pb均产生拮抗效应。富集系数有显著意义。4种藓类植物对Cu、Cd和Pb的吸收能力均是同一水平,可以作为指示植物,构成藓类植物组合来鉴别富集Cu、Cd和Pb的矿区。可利用卷叶丛本藓作为特征植物降低矿区As的污染。     

Some modification in the assay of Fe2+ in 1–10, o-phenanthroline extracts of fresh plant tissues

Summary The over-estimation of Fe²⁺ by a spectrophotometer due to simultaneous extraction of certain colouring matter in o-phenanthroline extracts can be avoided by making determinations on an atomic absorption spectrophotometer. It is shown that estimates of iron by atomic absorption spectrophotometer did not include measurable amount of Fe³⁺ due to a high specificity of o-phenanthroline for plant Fe²⁺.     

A high performance micro-dual-wavelength-spectrophotometer (MDWS)

The dual wavelength spectrophotometer (DWS) has proven to be the most sensitive device to monitor minute optical absorbance changes, which are inaccessible to conventional single or double beam spectrophotometers. The typical set ups, e.g. extensively used for Ca2+ or phytochrome measurements, are huge, expensive and cumbrous. Therefore, a novel high performance micro-dual-wavelength spectrophotometer (MDWS) was developed. It is miniaturized and no moving parts such as vibrational mirrors or rotating filter wheels involved. Its specifications are superior compared to the conventional set up being capable of detecting minute optical changes (reflection, absorbance, transmittance) at particular wavelengths.     

A multipurpose, fast scan spectrophotometer for measuring turbid (biological) materials

A new optical spectrophotometer has been developed, based on a recently patented monochromator for spectral measurements of clear and, in particular, of turbid materials in the millisecond time range. The number of optical and mechanical components of the spectrophotometer has been reduced to a minimum, resulting in excellent light throughput, a low stray-light level, low cost, compactness and rigidity. The spectrophotometer has been designed for all kinds of spectral measurements such as absorption, transmission, reflection and luminescence/radiation in a single-beam mode as documented by several examples. In principle, there is no restriction of wavelengths, ranging from UV to NIR and up to the IR range. As many functions as possible are relocated from the hardware to the software part of the design, which allows for extraordinary flexibility and simplicity. An appropriate computer program providing data acquisition, control and calibration functions as well as real-time display of spectra has been developed on the basis of a compiler language; indispensable “fast routines” are written in assembler language.Presented at the joint meeting of the German Botanical Society and the German Zoological Society entitled: Spectroscopy and Optical Techniques in Animal and Plant Biology, Münster, 30th Sept-3rd October 1996     

Design and operation of an adapter for the measurement of platelet aggregation with a spectrophotometer

The design and use of a special cell carriage for the turbidimetric measurement of platelet aggregation with a Cary 14 spectrophotometer are described. The resulting apparatus is far more versatile than commercially available aggregometers.     

An inexpensive computerized enzyme kinetics system based on a Gilford spectrophotometer and an Apple IIe microcomputer

A microcomputer-controlled data acquisition system for spectrophotometric enzyme kinetics measurements has been assembled. The system uses an Apple IIe computer which is interfaced to the binary coded decimal output of a Gilford spectrophotometer. No analog-to-digital converter had to be purchased. A BASIC program which collects timed absorbance readings every 500 ms, plots the data in real time, performs a linear regression of the data to measure the reaction rate, and calculates the enzyme activity concentration is given in full. Details describing the interfacing of the computer to the spectrophotometer are presented which will permit other laboratories to readily assemble their own systems using this hardware. Kinetic data acquired by the system are highly reproducible and agree well with data processed much more slowly by manual techniques from strip chart recordings.     

Hydroxyapatite column chromatography in procedures for isolation of purified DNA

Two spectrophotometer equipments especially adapted for experiments of enzyme-catalyzed reactions at subzero temperatures are described. Performance data as well as two typical applications of this technique are given and discussed.     

Development of a new device for on-line measurement of high cell concentrations

A variable-light-path-length flow-through cell to be installed on a spectrophotometer was developed for on-line measurement of high cell concentrations. Cell concentrations of up to about 100 g l^–1 could be measured without dilution. High concentration of protein solution was also measured. A spectrophotometer system combined with the flow-through cell is considered to be cost effective and durable with a minimal maintenance requirement.     

The colorimetric estimation of protein by the Lowry technique using a liquid scintillation counter

A comparison has been made of the use of the spectrophotometer and liquid scintillation counter for the colorimetric quantification of protein. The attenuation of photon detection from sealed miniature ¹⁴C radioactive standards enabled protein quantification over a concentration range far in excess of that achievable by the use of a spectrophotometer. Accuracy of quantification was high over the entire range of protein concentration. The ability of the technique to provide quick and accurate protein estimations is discussed.     

Determination of enzyme kinetic parameters by continuous addition of substrate to a single reaction mixture and analysis by a tangent-slope procedure: II. Application of the method to soluble and immobilized enzymes

A system is described for semiautomated evaluation of enzyme kinetic parameters, S_0.5, V, and Hill n. It consists of a Gilford spectrophotometer modified for continuous addition of substrate to a stirred enzyme assay mixture, and for recording of absorbance data coded on paper tape. The Hill parameters for a number of enzymes, obtained from these data by tangent-slope or curve-fitting procedures, are in good agreement with published or manually determined values. Experiments with rabbit muscle lactate dehydrogenase covalently linked to Sephadex G-50 or Sepharose 4B demonstrate the feasibility of this approach when applied to enzymes attached to solid supports. Instrumental errors due to spectrophotometer nonlinearity and drift, stirring, mixing, pumping, truncation in readout of absorbance, and bias in experimental parameters are minimal and do not significantly interfere with the method. The advantages and disadvantages of the approach are discussed, and improvements and extensions are suggested for the instrumental and data handling system which could greatly extend its utility.     

ZnO nanoparticles assist the refolding of denatured green fluorescent protein

Proteins are essential for cellular and biological processes. Proteins are synthesized and fold into the native structure to become active. The inability of a protein molecule to remain in its native conformation is called as protein misfolding, and this is due to several environmental factors. Protein misfolding and aggregation handle several human diseases. Protein misfolding is believed to be one of the causes of several disorders such as cancer, degenerative diseases, and metabolic pathologies. The zinc oxide (ZnO) nanoparticle was significantly promoted refolding of thermally denatured green fluorescent protein (GFP). In the present study, ZnO nanoparticles interaction with GFP was investigated by ultraviolet ‐ visible spectrophotometer, fluorescence spectrophotometer, and dynamic light scattering. Results suggest that the ZnO nanoparticles significantly assist the refolding of denatured GFP. Copyright © 2015 John Wiley & Sons, Ltd.     

不同生态环境中铜绿丽金龟幼虫肠道细菌产消化酶活性比较

目的 测定不同生态环境中铜绿丽金龟幼虫肠道细菌产消化酶活性。方法 采用平板透明圈法和分光光度计法。结果 平板透明圈法测得废弃菜园和花生田中铜绿丽金龟幼虫肠道细菌产蛋白酶和淀粉酶活性差异无统计学意义（F=1.089、0.4963,P>0.05）,而细菌的产纤维素酶活性有显著差异,其中花生田铜绿丽金龟幼虫肠道中分离到的粘质沙雷菌产酶活性显著高于其他菌株;分光光度计测得的不同生态环境中铜绿丽金龟幼虫肠道细菌的产蛋白酶、淀粉酶和纤维素酶活性差异均有统计学意义（F=461.565、42.349、18.7673,P<0.05）。从变异系数来看,分光光度计法测得的蛋白酶、淀粉酶和纤维素酶的变异程度较低,而脂肪酶测定时平板透明圈法的变异系数较低。结论 平板透明圈法和分光光度计法均可用于铜绿丽金龟幼虫肠道细菌产消化酶活性测定。通过分析研究比较,分光光度计法适于测定细菌的产蛋白酶、淀粉酶和纤维素酶活性,平板透明圈法适于测定细菌的产脂肪酶活性。     

Vesiculation of bovine erythrocyte membranes: two methods of quantification

Two simple methods of quantification of the relative concentration of vesicles released from bovine erythrocyte membranes are described. Turbidimetric and nephelometric measurements need only a typical spectrophotometer and spectrofluorimeter and could be employed for studying not only vesicles, but the turbidity of various suspensions.     

Lowry protein assay using an automatic microtiter plate spectrophotometer

The method of protein determination reported by Lowry et al. (1951, J. Biol. Chem. 193, 265-275) has been adapted for use with 96-well microtiter plates and an automatic microplate spectrophotometer. The spectrophotometer has been interfaced with a computer which plots the standard curve and calculates the protein content of each sample. The adapted method offers advantages over previously reported methods in that it is more rapid and uses a smaller sample volume (100 microliters) for samples containing 3-300 micrograms/ml (0.3-30 micrograms/assay) of protein. The method of Bensadoun and Weinstein (1976, Anal. Biochem. 70, 241-252) for precipitating microgram amounts of protein away from substances which interfere with the Lowry assay has also been adapted to this microplate procedure. These techniques should be particularly useful for laboratories where large numbers of samples containing a wide range of protein concentrations are assayed.     

An integrating atomic absorption spectrophotometer for ultramicroanalysis of metals

An integrating atomic absorption spectrophotometer for ultramicroanalysis of metals is described. The apparatus is intended mainly for determination of calcium and magnesium but can also be used for sodium, potassium, lithium, and copper, among other metals. Analyses of sample volumes as small as about 1 nl, containing calcium and magnesium in amounts as low as 10^?11 and 10^?12 moles, respectively, have been made. In analyses of samples containing 4·10^?12 moles of magnesium a coefficient of variation of ±5% was obtained.The principles of the apparatus are the same as for a conventional atomic absorption spectrophotometer apart from the fact that an electronic integrator with a rapid response has been used as the recording system. For atomization of the sample a hydrogen-air flame has been used in combination with a flame adapter. The sample is introduced into the flame by means of a small loop on a platinum-iridium filament.     

A stopped-flow dual-wavelength spectrophotometer suitable for the study of respiratory chains.

The requirements for a dual-wavelength stopped-flow spectrophotometer to be suitable for studying limited quantities of respiratory-chain preparations are described. They can be met by a design using mainly commercially available components. The constructed apparatus has a dead-time of approx. 2.6 ms, a mixing ratio of 17:1, and a minimal requirement for 0.5 ml of mixed reactants per flow.     

Direct spectrophotometric analysis of hemoglobin in isoelectric focusing tube gels

Methods are described for the direct spectrophotometric analysis of human oxyhemoglobin, deoxyhemoglobin, and methemoglobin focused in polyacrylamide tube gels. Visible absorption spectra (350-650 nm) of electrofocused hemoglobin bands were recorded using a diode array rapid-scan spectrophotometer. Direct optical sampling of gels allowed the identification of focused hemoglobin valency hybrids which contain two oxidized monomers per tetramer.     

Evaluation of redox indicators and the use of digital scanners and spectrophotometer for quantification of microbial growth in microplates

The growth indicators 2,3,5-triphenyltetrazolium chloride (TTC), 2-[4-iodophenyl]-3-[4-dinitrophenyl]-5-phenyltetrazolium chloride (INT), 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt (XTT), 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), and resazurin were tested for their ability to indicate bacterial growth/growth inhibition. Two reading devices were evaluated and compared, a microplate spectrophotometer and a digital flatbed scanner. The bacteria used in the study were cultivated in 96-wells microplates and readings were made after 24 h. The scanned pictures were analysed with a software developed in-house to generate numerical values. It was found that resazurin was difficult to use since it shifts between three colours. MTT and TTC had a high correlation between the spectrophotometer data and the data from the scanned images. The reproducibility was similar for both reading devices. In no case was there a need to resuspend the pellets before reading. Both the XTT and INT showed lower correlations.It is concluded that bacterial growth/growth inhibition can be easily and reproducibly measured from microplate cultivations with a flatbed scanner or with a microplate spectrophotometer.