Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Biochemistry

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gel electrophoresis, this is one of the methods used to deter-

mine the molecular weight of biomolecules. If the stationary

material is charged, the chromatography column will allow

separation of biomolecules according to their charge, a

process known as ion exchange chromatography. This process

provides the highest resolution in the purification of native

biomolecules and is valuable when both the purity and the

activity of a molecule are of importance, as is the case in the

preparation of all enzymesused in molecular biology. The bio-

logical activity of biomolecules has itself been exploited to

design a powerful separation method known as affinity chro-

matography. Most biomolecules of interest bind specifically

and tightly to natural biological partners called ligands:

enzymes bind substrates and cofactors, hormones bind recep-

tors, and specific immunoglobulinscalled antibodies can be

made by the immune systemthat would in principle interact

with any possible chemical component large enough to have a

specific conformation. The solid material in an affinity chro-

matography column is coated with the ligand and only the bio-

molecule that specifically interact with this ligand will be

retained while the rest of a mixture is washed away by excess

solvent running through the column.

Once a pure biomolecule is obtained, it may be

employed for a specific purpose such as an enzymatic reaction,

used as a therapeutic agent, or in an industrial process.

However, it is normal in a research laboratory that the biomol-

ecule isolated is novel, isolated for the first time and, therefore,

warrants full characterization in terms of structure and func-

tion. This is the most difficult part in a biochemical analysis of

a novel biomolecule or a biochemical process, usually takes

years to accomplish, and involves the collaboration of many

research laboratories from different parts of the world.

Recent progress in biochemical analysis techniques has

been dependant upon contributions from both chemistry and

biology, especially molecular geneticsand molecular biology,

as well as engineering and information technology. Tagging of

proteins and nucleic acids with chemicals, especially fluores-

cent dyes, has been crucial in helping to accomplish the

sequencing of the human genome and other organisms, as well

as the analysis of proteins by chromatography and mass spec-

trometry. Biochemical research is undergoing a change in par-

adigm from analysis of the role of one or a few molecules at a

time, to an approach aiming at the characterization and func-

tional studies of many or even all biomolecules constituting a

cell and eventually organs. One of the major challenges of the

post-genome era is to assign functions to all of the geneprod-

ucts discovered through the genome and cDNA sequencing

efforts. The need for functional analysis of proteins has

become especially eminent, and this has led to the renovated

interest and major technical improvements in some protein

separation and analysis techniques. Two-dimensional gel elec-

trophoresis, high performance liquid and capillary chromatog-

raphy as well as mass spectrometry are proving very effective

in separation and analysis of abundant change in highly

expressed proteins. The newly developed hardware and soft-

ware, and the use of automated systems that allow analysis of

a huge number of samples simultaneously, is making it possi-

ble to analyze a large number of proteins in a shorter time and

with higher accuracy. These approaches are making it possible

to study global protein expression in cells and tissues, and will

allow comparison of protein products from cells under varying

conditions like differentiation and activation by various stim-

uli such as stress, hormones, or drugs. A more specific assay

to analyze protein function in vivois to use expression systems

designed to detect protein-protein and DNA-protein interac-

tions such as the yeastand bacterial hybrid systems. Ligand-

receptor interactions are also being studied by novel

techniques using biosensors that are much faster than the con-

ventional immunochemical and colorimetric analyzes.

The combination of large scale and automated analysis

techniques, bioinformatic tools, and the power of genetic

manipulations will enable scientists to eventually analyze

processes of cell function to all depths.

See also Bioinformatics and computational biology;

Biotechnology; Fluorescence in situhybridization; Immuno-

logical analysis techniques; Luminescent bacteria

BBiochemistryIOCHEMISTRY

Biochemistry seeks to describe the structure, organization, and

functions of living matter in molecular terms. Essentially two

factors have contributed to the excitement in the field today

and have enhanced the impact of research and advances in bio-

chemistry on other life sciences. First, it is now generally

accepted that the physical elements of living matter obey the

same fundamental laws that govern all matter, both living and

non-living. Therefore the full potential of modern chemical

and physical theory can be brought in to solve certain biolog-

ical problems. Secondly, incredibly powerful new research

techniques, notably those developing from the fields of bio-

physics and molecular biology, are permitting scientists to ask

questions about the basic process of life that could not have

been imagined even a few years ago.

Biochemistry now lies at the heart of a revolution in the

biological sciences and it is nowhere better illustrated than in

the remarkable number of Nobel Prizes in Chemistry or

Medicine and Physiology that have been won by biochemists

in recent years. A typical example is the award of the 1988

Nobel Prize for Medicine and Physiology, to Gertrude Elion

and George Hitchings of the United States and Sir James

Black of Great Britain for their leadership in inventing new

drugs. Elion and Hitchings developed chemical analogs of

nucleic acids and vitamins which are now being used to treat

leukemia, bacterial infections, malaria, gout, herpes virus

infections and AIDS. Black developed beta-blockers that are

now used to reduce the risk of heart attack and to treat diseases

such as asthma. These drugs were designed and not discovered

through random organic synthesis. Developments in knowl-

edge within certain key areas of biochemistry, such as protein

structure and function, nucleic acid synthesis, enzyme mecha-

nisms, receptors and metabolic control, vitamins, and coen-

zymes all contributed to enable such progress to be made.

Two more recent Nobel Prizes give further evidence for

the breadth of the impact of biochemistry. In 1997, the

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