Science Progress (2001), 84 (1)

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Science Progress (2001), 84 (1), 1–16

The origin of life I:

When and where did it begin?

PAUL DAVIES

For decades most scientists assumed that life emerged billions of years ago

in a “primordial soup” somewhere on the Earth’s surface. Evidence is

mounting, however, that life may have begun deep beneath the surface, perhaps

near a volcanic ocean vent or even inside the hot crust itself. Since

there are hints that life’s history on Earth extends back through the phase

of massive cosmic bombardment, it may be that life started on Mars and

came here later, perhaps inside rocks ejected from the Red Planet by large

impacts. The traffic of intact rocks between Mars and Earth is now an

established fact, and experiments confirm that microbes could survive the

rigours of the journey through space if cocooned within such material.

Unfortunately, this planetary cross-contamination compromises astrobiologists’

hope of finding a second genesis in the solar system.

Science Progress (2001), 84 (1), 17–29

The origin of life II:

How did it begin?

PAUL DAVIES

The problem of how a mixture of chemicals can spontaneously transform

themselves into even a simple living organism remains one of the great outstanding

challenges to science. Various primordial soup theories have been

proposed in which chemical self-organization brings about the required

level of complexity. Major conceptual obstacles remain, however, such as

the emergence of the genetic code, and the “chicken-and-egg” problem

concerning which came first: nucleic acids or proteins. Currently fashionable

is the so-called RNA world theory, which casts RNA in the role of both

chicken and egg. Other theories assume that protein chemistry and even

clay crystal life came before nucleic acids. To be fully successful, a theory

of biogenesis has to explain not merely the emergence of molecular replication

and chemical complexity, but the crucial information content and

information processing capabilities of the living cell.

Science Progress (2001), 84 (1), 45–68

Use of EPR spectroscopy to

study macromolecular structure

and function

ROOPA BISWAS, HENRIETTE KÜHNE, GARY W. BRUDVIG AND

VENKAT GOPALAN

Electron paramagnetic resonance (EPR) spectroscopy is now part of the

armory available to probe the structural aspects of proteins, nucleic acids

and protein–nucleic acid complexes. Since the mobility of a spin label

covalently attached to a macromolecule is influenced by its microenvironment,

analysis of the EPR spectra of site-specifically incorporated spin

labels (probes) provides a powerful tool for investigating structure–function

correlates in biological macromolecules. This technique has become

readily amenable to address various problems in biology in large measure

due to the advent of techniques like site-directed mutagenesis, which

enables site-specific substitution of cysteine residues in proteins, and the

commercial availability of thiol-specific spin-labeling reagents (Figure 1)1.

In addition to the underlying principle and the experimental strategy,

several recent applications are discussed in this review.

Science Progress (2001), 84 (1), 000–000

Relics: penguin population

programs

LIGUANG SUN AND ZHOUQING XIE

What has been responsible for the increase in Chinstrap penguin populations

during the past 40 years in maritime Antarctica? One view ascribes it to an

increase in availability of their prey brought on by the decrease in baleen

whale stocks. The contrary opinion, attributes it to environmental warming.

This causes a gradual decrease in the frequency of cold years with extensive

winter sea ice cover. A number of penguin monitoring programs are in

progress and are expected to provide some answers to these questions.

Unfortunately, it is not easy to distinguish natural variability from anthropogenic

change since penguins are easily accessible predators of krill and

the feeding range of the penguins has almost overlapped with the krill fishery

in time and space in the last four decades. Therefore it is important to reconstruct

the change of ancient penguin abundance and distribution in the

absence of human activity. Many efforts have focused on surveying the abandoned

penguin rookeries, but this method has not been able to give a continuous

historical record of penguin populations. In several recent studies, ancient

penguin excreta was scooped from the penguin relics in the sediments of the

lake on penguin rookery, Ardley Island, maritime Antarctica. In these studies,

penguin droppings or guano soil deposited in the lake and changes in sediment

geochemistry have been used to calculate penguin population changes

based upon the geochemical composition of the sediment core. The results

suggest that climate change has a significant impact on penguin populations.

Science Progress (2001), 84 (1), 69–85

Safety aspect concerning

radiolytic gas generation in

reactors

V. RAMSHESH

In water cooled and water moderated reactors (H2O in boiling water

reactors/pressurised water reactors, D2O in pressurised heavy water reactors)

during normal operation, radiolysis is a source of production of

hydrogen/deuterium and oxygen. During the progress of a nuclear accident,

while there are other important sources of hydrogen/deuterium, the

oxygen availability can occur only through radiolysis or direct contact with

air. In air saturated with water vapour at room temperature and pressure

when H2/D2 concentration exceeds 4 vol % (a conservative estimate), a

combustible mixture with oxygen can be formed. It is proposed to examine

the basic principles of water radiolysis as far as they pertain to generation

of H2/D2 and O2 and try to apply these concepts to reactors both under

operating conditions and in accident situations. It is concluded that the

possibility of an accident taking place through radiolysis is highly unlikely.