Current
Medicinal Chemistry
ISSN: 0929-8673
Current Medicinal Chemistry
Volume 12, Number 22, 2005
Contents
Confocal Fluorescence Microscopy for High-Throughput
Screening of G-Protein Coupled Receptors Pp. 2551-2559
Ralf Heilker, Lenka Zemanova, Martin J. Valler and
G. Ulrich Nienhaus
[Abstract]
Peptide Nucleic Acids (PNAs), A Chemical Overview
Pp. 2561-2599
Andrea Porcheddu and Giampaolo Giacomelli
[Abstract]
Mechanism of Mitochondrial Uncouplers, Inhibitors,
and Toxins: Focus on Electron Transfer, Free Radicals, and
Structure -Activity Relationships Pp. 2601-2623
Peter Kovacic, Robert S. Pozos, Ratnasamy Somanathan,
Nandita Shangari and Peter J. O’Brien
[Abstract]
Medicinal Plants with Inhibitory Properties Against
Snake Venoms Pp. 2625-2641
Andreimar M. Soares, Fábio K. Ticli, Silvana Marcussi,
Miriam V. Lourenço, Ana Helena Januário, Suely
V. Sampaio, JosŽ R. Giglio, Bruno Lomonte and Paulo
S. Pereira
[Abstract]
Current Status of Malaria Control Pp. 2643-2659
R.P. Tripathi, R.C. Mishra, N. Dwivedi, N. Tewari and
S.S. Verma
[Abstract]
Abstracts
[Back to top]
Confocal Fluorescence Microscopy for High-Throughput Screening
of G-Protein Coupled Receptors
Ralf Heilker, Lenka Zemanova, Martin J. Valler and
G. Ulrich Nienhaus
In the pharmaceutical industry, G-protein coupled receptors
(GPCRs) are the most successful group of therapeutic targets.
Finding compounds that interfere with the ligand-GPCR interaction
in a specific and selective way is a major focus of pharmaceutical
research today. As compound libraries of large pharmaceutical
companies have increased to hundreds of thousands of test
compounds, there is a growing need for miniaturization of
drug discovery assays to save bioreagents and to reduce the
consumption of test compounds.
Due to its high sensitivity combined with a femtoliter-sized
measurement volume, confocal fluorescence microscopy enables
designs for GPCR binding assays with tiny sample volumes.
The GPCRs are prepared in the form of plasma membrane fragments
from GPCR-overexpressing cells or may be integrated into virus-like
particles (VLiPs). One technique to extract binding data from
confocal fluorescence experiments is the so-called fluorescence
intensity distribution analysis (FIDA). In this review article,
we describe the applicability of FIDA to GPCR-focussed high-throughput
screening (HTS) and compare FIDA to two other GPCR-adaptable
drug discovery techniques for ligand binding studies, the
scintillation proximity assay (SPA) and macroscopic fluorescence
polarization (FP) measurements. FIDA measures the absolute
concentrations of both GPCR-bound and unbound ligand, thereby
providing an internal control to the drug screening data.
FIDA is amenable to work with relatively low amounts of GPCRs
so that the assay may be carried out with biomembranes of
a low GPCR density. Moreover, the fluorescence intensity readout
of the FIDA technique may be combined with other confocal
fluorescence readouts such as fluorescence anisotropy or lifetime.
The combination of a low sample volume with an information-rich
measurement means that confocal fluorescence spectroscopy
can bring substantial benefits as a bioassay platform to pharmaceutical
GPCR-directed research.
[Back to top]
Peptide Nucleic Acids (PNAs), A Chemical Overview
Andrea Porcheddu and Giampaolo Giacomelli
Peptide nucleic acid (PNA) is a nucleic acid analogue and
a fully synthetic DNA/RNA-recognising ligand with a neutral
peptide-like backbone. In spite of the large change on the
backbone structure, PNA molecules bind strongly to complementary
DNA and RNA sequences. Originally conceived as ligand for
the recognition of double stranded DNA, the unique physico-chemical
properties of PNAs have led to the development of a variety
of research and diagnostic assays. The extraordinary properties
of PNA may advance routine clinical tests and environmental
analyses that will utilise the PNA technology. PNAs may also
have an impact on in situ hybridisation, cytogenetics and
industrial microbiology. This paper presents some recent achievements
on peptide nucleic acids and discusses, from the viewpoint
of literature, what the potential is and what the limitations
of such compounds are. This review, which is not intended
to be exhaustive, is mostly aimed at the current progress
in PNA chemistry, structure, and hybridisation, highlighting
some applications too.
[Back to top]
Mechanism of Mitochondrial Uncouplers, Inhibitors, and
Toxins: Focus on Electron Transfer, Free Radicals, and Structure
-Activity Relationships
Peter Kovacic, Robert S. Pozos, Ratnasamy Somanathan,
Nandita Shangari and Peter J. O’Brien
The biology of the mitochondrial electron transport chain
is summarized. Our approach to the mechanism of uncouplers,
inhibitors, and toxins is based on electron transfer (ET)
and reactive oxygen species (ROS). Extensive supporting evidence,
which is broadly applicable, is cited. ROS can be generated
either endogenously or exogenously. Generally, the reactive
entities arise via redox cycling by ET functionalities, such
as, quinones (or precursors), metal compounds, imines (or
iminiums), and aromatic nitro compounds (or reduced metabolites).
In most cases, the ET functions are formed metabolically.
The toxic substances belong to many categories, e.g., medicinals,
industrial chemicals, abused drugs, and pesticides. Structure-activity
relationships are presented from the ET-ROS perspective, and
also quantitatively. Evidence for the theoretical framework
is provided by the protective effect of antioxidants. Among
other topics addressed are proton flux, membrane pores, and
apoptosis. There is support for the thesis that mitochondrial
insult may contribute to illnesses and aging.
[Back to top]
Medicinal Plants with Inhibitory Properties Against Snake
Venoms
MAndreimar M. Soares, F‡bio K. Ticli, Silvana
Marcussi, Miriam V. Loureno, Ana Helena Janu‡rio,
Suely V. Sampaio, JosŽ R. Giglio, Bruno Lomonte and
Paulo S. Pereira
Envenomations due to snake bites are commonly treated by
parenteral administration of horse or sheep-derived polyclonal
antivenoms aimed at the neutralization of toxins. However,
despite the widespread success of this therapy, it is still
important to search for different venom inhibitors, either
synthetic or natural, that could complement or substitute
for the action of antivenoms. Several plants have been utilized
in folk medicine as antiophidian. However, only a few species
have been scientifically investigated and still less had their
active components isolated and characterized both structurally
and functionally. This article presents a review of plants
showing neutralizing properties against snake venoms which
were assayed in research laboratories, correlating them with
ethnopharmacological studies, as (i) the part of the plant
used as antidote, (ii) its respective genus and family and
(iii) inhibition of the main pharmacological, toxic and enzymatic
activities of snake venoms and isolated toxins. Protective
activity of many of these plants against the lethal action
of snake venoms has been confirmed by biological assays. Compounds
in all of them belong to chemical classes capable of interacting
with macromolecular targets (enzymes or receptors). Popular
culture can often help to guide scientific studies. In addition,
biotechnological application of these inhibitors, as helpful
alternative or supplemental treatments to serum therapy, and
also as important models for synthesis of new drugs of medical
interest, needs to be better oriented and scientifically explored.
[Back to top]
Current Status of Malaria Control
R.P. Tripathi, R.C. Mishra, N. Dwivedi, N. Tewari and
S.S. Verma
Malaria caused by Plasmodium parasites kills approximately
1-3 million people and causes disease in 300-500 million people
annually throughout the world. The current approaches to curtail
this disease include vector control, vaccination, immunotherapy
and chemotherapy. The vector control is achieved by reducing
vector density, interrupting their life cycle, and creating
a barrier between the human host and mosquitoes. A number
of vaccine candidates are being clinically tried and R&D
effort in this direction is coming in a big way. Currently
there are only limited safe drugs for the treatment of this
disease, however, reports of emerging resistance against existing
drugs warrant the introduction of new drugs, which are unlikely
to come from pharmaceutical industries because of limited
commercial opportunities.
One of the most important current approaches to develop
new drugs involves the synthesis of chemical libraries and
evaluate them against most validated biochemical targets of
malarial parasite. Although a number of such targets in antimalarial
drug development are known today, yet only validated and selective
biochemical targets including mitochondrial transport, glycolic
pathway, folate pathway, proteases and heme metabolism, apicoplast
metabolism, glycophospatidyl inositol, lipid metabolism (glycerophospholipids),
peptidyl deformylase and oxidative stress in parasite-infected
erythrocytes have been discussed here.
The well known antimalarial drugs and different drug combinations
for the treatment of malaria are also briefly reviewed. A
survey of the recently discovered new molecules active against
malaria has also been narrated. Lastly, the future of malaria
chemotherapy and new directions emerging from literature has
been elucidated.
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