Enzymatic determination of the major serum lipids with a common indicator reaction

Enzymatic, colorimetric assays for serum cholesterol, choline-containing phospholipids, and triglycerides were developed with the intent of being able to specifically determine these individual lipids after isolation of serum lipoproteins by a technology such as ultracentrifugation that is already developed, electrophoresis that is already available for cholesterol and awaits the other lipid stains, or chemical fractionation. Once the relative amounts of the lipids in each lipoprotein fraction are known, the absolute amounts in each separated fraction can then be calculated using the total serum concentrations. As a secondary purpose, the measurement and arithmetic summation of serum cholesterol, choline-containing phospholipids, and triglycerides concentrations appears to provide a close estimate of the major serum total lipids. This summation technique results in apparent lower serum total lipids values than are obtained by a conventional turbidimetric method. This bias appears to be due to a combination of overestimation by the turbidimetric method and underestimation by the summation technique. However, this summation technique appears to be able to provide more information for specific lipid measurements on chemical, ultracentrifugal, or electrophoretic separation of lipoproteins by revealing which lipid class(es) is/are present in an abnormal concentration. It could also prove useful in providing major total lipid information for nonspecific staining of electrophoretic zones where fat-soluble stains such as Sudan black B are presently used. In the latter case, cholesterol and triglycerides are already determined and only the choline-containing phospholipid assay is additional.     

The spectrophotometric determination of copper with disodium 3-hydroxy-4-[(6-methyl-2-pyridyl)azo]-2,7-naphthalenedisulfonate N-oxide

Summary The synthesis and characterization of disodium 3-hydroxy-4-[(6-methyl-2-pyridyl)azo]-2, 7-naphthalenedisulfonateN-oxide and its application to the spectrophotometric determination of trace amounts of copper are described. The effects due to pH, time, reagent concentration and diverse ions are reported. The reagent exhibits good specificity for copper. Beer's law is obeyed and the molar absorbance coefficient at 536 nm is 1.8×10⁴.

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Die spektrophotometrische Bestimmung von Kupfer mit Dinatrium-3-hydroxy-4-[(6-methyl-2-pyridyl)azo]-2, 7-napbthalindisulfonat-N-oxid

Zusammenfassung Die Synthese und die Eigenschaften von Dinatrium-3-hydroxy-4-[(6-methyl-2-pyridyl)azo]-2, 7-naphthalindisulfonat-N-oxid sowie dessen Anwendung zur spektrophotometrischen Bestimmung von Kupferspuren wurden beschrieben. Die Einflüsse von pH, Zeit, Reagenskonzentration und von verschiedenen Ionen wurden angegeben. Das Reagens zeigt gute Spezifität gegenüber Kupfer. Das Beersche Gesetz wird befolgt. Der molare Extinktionskoeffizient bei 536 nm beträgt 1,8·10⁴.

     

Selective Ruthenium Labeling of the Tryptophan Residue in the Bee Venom Peptide Melittin

Melittin is a membrane‐active peptide from bee venom with promising antimicrobial and anticancer activity. Herein we report on a simple and selective method for labeling of the tryptophan residue in melittin by the organometallic fragment [(C₅H₅)Ru]⁺ in aqueous solution and in air. Ruthenium coordination does not disturb the secondary structure of the peptide (as verified by 2D NMR spectroscopy), but changes the pattern of its intermolecular interactions resulting in an 11‐fold decrease of hemolytic activity. The high stability of the organometallic conjugate allowed the establishment of the biodistribution of the labeled melittin in mice by inductively coupled plasma MS analysis of ruthenium.     

Electrochemical method for the preparation nanocomposites based on carbon nanotubes and chromium oxides for oxygen electrodes

An electrochemical method for the preparation of nanostructured composites based on multiwalled carbon nanotubes and chromium oxide is proposed. The method involves electrodeposition of chromium oxides from a solution of hexavalent chromium oxide in sulfuric acid on carbon nanotubes. By varying the electrolysis conditions one can obtain deposited—catalyst particles of different size and vary the amount of catalyst. Oxygen electrodes have been made from the materials obtained for fuel cells with alkaline electrolyte, which showed good electrocatalytic properties.     

Serum iohexol analysis by micellar electrokinetic capillary chromatography

A simple and rapid ( approximately 4 min) method for the measurement of iohexol in serum for assessing the glomerular filtration rate is described. It is based on direct serum injection on the capillary by MEKC. The method is linear between 8 and 260 mg/L, with an RSD of peak height of 2.9%. Several simple steps have contributed to an improved daily precision, such as choosing a high pH buffer, increasing the SDS concentration, frequent standardization, and eliminating any sample pretreatment.     

Validation of reducing-difference procedure for the interpretation of non-polarized infrared spectra of n-component solid mixtures

Validation of reducing-difference procedure based on subtracting of non-polarized infrared (IR) spectra of n-component solid mixtures is presented. The accuracy and precision are established. The limits of detection are 3.0, 2.5, 1.5 and 1.0 wt.% for 5-, 4-, 3-and 2-component mixtures, respectively. Smoothing procedures for IR spectral analysis, based on Savitzky-Golay or Fourier methods are applied as well. The mean values and relative standard deviations for peak position (ν_i) and integral absorbance (A_i) obtained by this data processing approach have been examined using Student's t-test.     

Capillary electrophoresis of the proteolytic activity of the stratum corneum obtained by tape stripping

Serine proteases and some cathepsins are present in the stratum corneum. They are known to play a significant role in the pathophysiological mechanism of several dermatological conditions (e.g. atopic dermatitis) and in the induction of itch. Tape stripping of skin is a simple technique used in the investigation of skin barrier function and in the penetration of topically applied drugs. Herein, we show that CE, under stacking conditions, is a well-suited technique to measure the proteolytic activity of enzymes in the stratum corneum. Disks of about 6 mm (id) were cut from adhered tapes and submerged directly in a buffer containing the appropriate peptide substrate. After incubation, the split peptides were separated and detected directly by CE at 214 nm in a borate buffer. The esterase activity on N-benzoyl-tyrosine ethyl ester and the amidase activity on succinyl-Ala-Ala-Pro-Phe-p-nitroanilide and the splitting of hemoglobin were detected by CE. The esterase activity was the highest when compared to the proteolytic activities. Skin scratching increased the enzymatic activity adhered to the tapes. The CE offered over the traditional end-point colorimetric methods the ability to measure the low enzymatic activity and the ability to detect the released peptides directly. This technique is simple, non-invasive, easy to perform and uses non-expensive substrates. It can be useful in quantifying cathepsins and serine proteases in the skin.