Biomedical subjects

K Markides

Publications and source records attributed to K Markides.

6 recordsLinked to original sources

PubMed2000

Optimization of capillary electrophoresis conditions for coupling to a mass spectrometer via a sheathless interface.

When optimizing a capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI-MS) system, consideration has to be given not only to the separation but also to the electrospray stability. Methods developed for CE/UV analysis of drugs and peptides were considered and modified to be suitable for a CE/MS system with a robust sheathless interface. Different concentrations of the organic modifiers acetonitrile, methanol and 2-propanol were used in the separation buffer. The type and concentrations of these modifiers were also compared with reference to electrospray stability, sensitivity and time of analysis. In addition, different ionic strengths in the buffers were evaluated with reference to electrospray stability. The repeatability was used for the estimation of electrospray stability. The degree to which these parameters influenced the separation and the ESI stability was studied using a nine-peptide standard mixture and the antibiotic drugs bacampicillin and ampicillin as test substances. The analysis time and resolution were used as measures of the efficiency of the separation. A time-of-flight MS analyzer was used since it has the potential advantages of becoming a better fit for integration of CE with MS owing to the speed and sensitivity of this mass analyzer. The detection limit, i.e. 1 microM, for bacampicillin was comparable to what could be achieved with CE/MS on a quadrupole instrument using selected ion monitoring and sheath flow ESI.

Electrophoresis, Capillary↗

PubMed2000

Current awareness.

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Books, Reviews & Symposia; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (5 Weeks journals - Search completed at 27th. Apr 2000)

Bibliographies as Topic↗

PubMed2000

Analysis of enzymatically digested proteins and protein mixtures using a 9.4 Tesla Fourier transform ion cyclotron mass spectrometer.

A commercially available 9.4 Tesla Fourier transform ion cyclotron resonance (FTICR) mass spectrometer was applied in the analysis of tryptic digests of protein mixtures without any separation. First, the method was demonstrated on a mixture of tryptic digests of equine cytochrome c, equine myoglobin and bovine serum albumin. The same method was then applied to human plasma from a healthy blood donor. Computer programs were employed to simplify analysis of the complex spectra. The 2745 peaks in the human plasma electrospray ionization FTICR spectrum could be reduced to 1165 isotopic clusters and 669 unique masses. Out of these, 82 masses matched tryptic fragments of serum albumin with mass measurement errors less than 10 ppm, covering 93% of the sequence. Another 16 masses were assigned to tryptic fragments of transferrin, covering 41% of the sequence on the 10 ppm mass measurement error level (14 within 2 ppm). The mass measurement errors were approximately normal distributed with a standard deviation of 1.7 ppm. This demonstrates the feasibility of combining the ultra-high mass resolving power and accuracy of FTICR mass spectrometry with automated computer analysis for investigating complex biological matrices.

Algorithms↗

PubMed1999

Compounds labelled with short-lived beta(+)-emitting radionuclides and some applications in life sciences. The importance of time as a parameter.

Some examples of recent development of the synthesis of compounds labelled with short-lived beta(+)-emitting radionuclides will be discussed with an emphasis on the importance of time in selecting a synthetic strategy. Furthermore the use of such labelled compounds to monitor certain processes in areas within the field of analytical chemistry and in various applications in drug development will be presented.

Animals↗

PubMed1990

Measuring social support among older adults.

The purpose of this study is to introduce a measure of natural supportive behaviors for use in studies that examine the relationship between stress, social support, and health among older adults. The index improves on existing measures in three ways: it avoids problems arising from confounding potentially supportive relationships with support that is actually received; the scale also assesses variations in individual support needs; and it measures four distinct dimensions of social support (informational support, tangible help, emotional support, and integration). Based on data from a random community survey of 351 older adults, the basic psychometric properties and the factor structure of the scale are explored. The predictive validity of the scale is demonstrated by showing that the dimensions of support buffer the stressful effects of bereavement on depressive symptoms.

Aged↗

PubMed1987

Illness of spouse and psychological well-being in older adults.

The purpose of this study is to determine whether illness of a spouse is a source of significant psychological distress for older adults. In addition, we also examine whether two intervening variables (chronic financial strain and chronic marital strain) might explain why this relationship exists. A final goal of this study was to determine whether gender differences exist in the relationships among these indicators. Findings from a random community survey of elderly people suggest that while illness of spouse exerts significant direct effects on depression for both older men and older women, the indirect effects through financial and martial strain are largely restricted to elderly women.

Aged↗