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Current Analytical Chemistry
ISSN: 1573-4110
Current Analytical Chemistry
Volume 3, Number 2, April 2007
Contents
Evaluation of Different Methods for Assaying
Protein Carbonylation Pp. 93-102
Filip Matthijssens, Bart P. Braeckman and Jacques R. Vanfleteren
[Abstract]
Modern Methods of Bile Acid Analysis by Mass
Spectrometry: A View into the Metabolome Pp. 103-126
Yuqin Wang and William J. Griffiths
[Abstract]
Nonparametric Pre-Processing Methods and Inference
Tools for Analyzing Time-of-Flight Mass Spectrometry Data
Pp. 127-147
Anestis Antoniadis, Jeremie Bigot, Sophie Lambert-Lacroix
and Frédérique Letué
[Abstract]
Headspace Analyses in Valuable and Functional Foods:
Application of SPME in the Quality Control and Characterization
of Olive Oils Pp. 149-159
Guido Flamini
[Abstract]
Calixarene HPLC Phases – Applications
Pp. 161-170
Rüdiger Meyer and Thomas Jira
[Abstract]
Abstracts
[Back to top]
Evaluation of Different Methods for Assaying Protein Carbonylation
Filip Matthijssens, Bart P. Braeckman and Jacques R. Vanfleteren
Most current methods for determining protein carbonyl
content are based on the reaction of carbonyl groups with
2,4-dinitrophenylhydrazine (DNPH) to form 2,4-dinitrophenylhydrazone
derivatives, which can then be detected and quantitated spectrophotometrically
or immunochemically.
In this article, we evaluate different quantitative and semi-quantitative
techniques for measuring protein carbonylation. We assessed
the sensitivity and accuracy of these techniques using both
test samples and tissue extracts.
We found that absorbance based quantitation of protein phenylhydrazone
content is prone to experimental variation, often generating
unreliable results. A previously described microplate ELISA
method enabled very sensitive and accurate meas-urement of
the carbonyl content of mixtures of reduced and oxidized BSA
but proved to be quite insensitive when complex biological
samples were assayed. Immunochemical detection and quantitation
of DNPH derivatized samples spotted onto nitrocellulose membrane
or processed using unifilter devices often produced inconsistent
results. The difficulties observed with each of these methods
appear to be associated with the presence of unreacted DNPH
and non-protein carbonyl. We found that short SDS-PAGE of
derivatized sample efficiently removes these confounding substances
and enables sensitive and reliable immunochemical detection
of protein carbonyl after electrophoretic transfer of the
proteins onto nitrocellulose membrane.
[Back to top]
Modern Methods of Bile Acid Analysis by Mass
Spectrometry: A View into the Metabolome
Yuqin Wang and William J. Griffiths
The advent of the “omics” revolution has reawakened
an interest in the mass spectrometric analysis of bile acids,
particularly in the related fields of lipidomics and metabolomics.
This is due to the presence of bile acids in body fluids and
their potential to act as biomarkers. Bile acids and bile
alcohols are formed from cholesterol in the liver. Bile acids
are excreted from the liver into the small intestine via the
bile duct conjugated with glycine or taurine at the side-chain
carboxyl group. After assisting in the lipolysis and absorption
of fats in the intestinal lumen, bile acids are returned to
the liver. Bile acids and bile alcohols undergo further metabolism
by bacterial and hepatic enzymes during the enterohepatic
circulation, including hydrolysis of conjugates, oxidation
and reduction, isomerisation, dehydroxylation and hydroxylation.
The hydroxyl groups may also be conjugated with sulphuric
acid, glucuronic acid, glucose or N-acetylglucosamine
in the liver and in extrachepatic organs including intestine
and kidney. Thus, the mixture of metabolic products of cholesterol
in biological fluids can be very complex. Here we describe
modern mass spectrometric methods used to characterise this
diverse range of molecules found in biological fluids.
[Back to top]
Nonparametric Pre-Processing Methods and Inference
Tools for Analyzing Time-of-Flight Mass Spectrometry Data
Anestis Antoniadis, Jeremie Bigot, Sophie Lambert-Lacroix
and Frédérique Letué
The objective of this paper is to contribute to the methodology
available for extracting and analyzing signal content from
protein mass spectrometry data. Data from Matrix-Assisted
Laser Desorption Ionization Time-of-Flight (MALDI-TOF) or
Surface-Enhanced Laser Desorption and Ionization Time-Of-Flight
(SELDI-TOF) spectra require considerable signal pre-processing
such as noise removal and baseline level error correction.
After removing the noise by an invariant wavelet transform,
we develop a background correction method based on penalized
spline quantile regression and apply it to MALDI-TOF spectra.
The results show that the wavelet transform technique combined
with nonparametric quantile regression can handle all kinds
of background and low signal-to-background ratio spectra;
it requires no prior knowledge about the spectra composition,
no selection of suitable background correction points, and
no mathematical assumption of the background distribution.
We further present a multi-scale based novel spectra alignment
methodology useful in a functional analysis of variance method
for identifying proteins that are differentially expressed
between different type tissues. Our approaches are compared
with several existing approaches in the literature and are
tested on simulated and real data. The results indicate that
the proposed schemes enable accurate diagnosis based on the
over-expression of a small number of identified proteins with
high sensitivity.
[Back to top]
Headspace Analyses in Valuable and Functional Foods:
Application of SPME in the Quality Control and Characterization
of Olive Oils
Guido Flamini
Virgin olive oil, obtained from Olea europaea L.
(Oleaceae) fruits, is an important ingredient in the Mediterranean
diet. There is now overwhelming scientific evidence that it
has health benefits; that include reduction of risk factors
for coronary heart disease and the prevention of several pathologies,
including some types of cancer. Olive oil appears to be an
example of a functional food with a high content of volatiles
that contribute to its palatability. However, because of its
high added value, it is often adulterated with less valuable
oils. Many analytical techniques have been developed to validate
the authenticity of the oil. Among them, SPME seems to be
one of the more promising approaches, as demonstrated by the
many published studies. Being a solvent-free sample preparation
technique, its implementation is fast and simple and couples
well with GC-MS and HPLC systems. These validation techniques
are very important considering the strict regulations imposed
by the USA and the EU. Finally, it can be helpful in geographical
certification, giving consumers the assurance that the goods
come from an area where a given quality, reputation, or other
characteristics of the goods is essentially attributable to
their geographical origin.
[Back to top]
Calixarene HPLC Phases – Applications
Rüdiger Meyer and Thomas Jira
Calixarenes, following cyclodextrines and crown ethers,
are the third generation of supramolecules used in HPLC as
stationary phases. They consist of phenol units linked via
methylene bridges and can also form inclusion complexes like
the other host supramolecules. The resulting interactions
influence the retention factors and improve the selectivity
of the solutes. Additionally, modification of the calixarenes,
for instance by varying the ring size, substitutents, conformations
and pKa values, enable a more enhanced interaction spectrum
and can improve the specificity for guest molecules.
The application of calixarenes in chromatography also includes
medical and environmental applications, preparative chemistry
as well as the rapidly developing area of supramolecular chemistry.
Taking the possibilities and the growing interests of calixarenes
into account, the aim of the review is to summarise the application
possibilities and interactions of calixarenes as stationary
phase in HPLC.
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