Science Progress (2001), 84 (2)

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Science Progress (2001), 84 (2), 87–104

Origin of feathers – perspectives

from fossil evidence

ZHONGHE ZHOU AND FUCHENG ZHANG

Introduction

Feathers are probably the most complex and fascinating integuments

of vertebrates. The issue of the origin of feathers has puzzled scientists

for over a century. Perhaps with the appearance of civilization and

culture, the fact feathers are a unique feature distinguishing birds

from reptiles has become as obvious to us as the day and night. This

is probably still the case for many of us, but most paleontologists

would now say “wait!” and tell you a different story. The secret they

believe they have discovered is that there existed feathered

dinosaurs. While ornithologists and paleontologists are still hotly

debating on the presence of feathers in several dinosaurs from China,

an international research group comprising ornithologists, paleontologists

and physiologists announced that they found feathers in a much

more ancient and primitive reptile, named Longisquama from

Kyrgyzstan. Only a few months earlier, Chinese paleontologists

reported an intermediate integumentary type between reptilian

scales and avian feathers in a primitive bird, named Protopteryx.

Science Progress (2001), 84 (2), 105–124

Environmental echoes

JOHN L. STANFORD, CYNTHIA A. STANFORD AND

JOHN M. GRANGE

Allergy, auto immunity and cancer are becoming more prevalent in the developed

world. One explanation might be that the immune system required to

protect us from such problems is being inadequately trained, perhaps due to

our increased separation from the environment which has shaped our mutating

genes since we emerged from the primaeval ooze. Those infections which

were the essential primers of our immunity are being prevented and action is

needed to refocus the immune response without exposing us to the diseases of

the past. In this paper we assess our place in relation to the environment and

consider ways in which the situation can be redressed. There are considerable

similarities between the immune system and human consciousness. Both

enter the world in considerable ignorance of the events awaiting them, yet

with the genetic ability, endowed by millennia of selection and evolution, to

experience the world, to interpret and act on the experiences and to retain

memory of the experiences. In both systems, maternal influences and early

environmental encounters have profound effects on determining the patterns

of subsequent responses. Ideally the ‘learned’ responses will benefit or protect

the individual but inappropriate responses may lead to self damage. As

the environment has altered irrevocably, attention must be paid to regulating

the balance of immunological responsiveness to that expected of the normal

immunological learning process. This should be possible by novel vaccination

strategies.

Science Progress (2001), 84 (2), 125–136

The serpins: nature’s molecular

mousetraps

JAMES A. HUNTINGTON AND ROBIN W. CARRELL

A special family of inhibitors, known as the serpins, has evolved an extraordinary

mechanism to enable the control of the proteolytic pathways

essential to life. The serpins undergo a profound change in conformation to

entrap their target protease in an irreversible complex. The solving of the

structure of this complex now completes a video depiction of the changes

involved. The serpin, just like a mousetrap, is seen to change with a springlike

movement from an initial metastable state to a final hyperstable form.

The structure shows how this conformational shift not only inhibits the

protease but also destroys it. A bonus from these structural insights is the

realisation that a number of diseases, as diverse as thrombosis, cirrhosis

and dementia, all share a common mechanism arising from similar mutations

of different serpins.

Science Progress (2001), 84 (2), 137–156

Photochemistry of photochromic

benzopyrans studied by timeresolved

absorption spectroscopy

TAKAKAZU NAKABAYASHI, NOBUYUKI NISHI AND

HIROCHIKA SAKURAGI

Photochromic reactions of 2H-benzopyrans have been extensively studied

to design new materials for commercial applications such as optical

memories. Photochromism of 2H-benzopyrans proceeds from a C–O bond

cleavage of the colorless closed form to give the colored open forms, which

can thermally revert back to the original closed form. From time-resolved

absorption spectroscopy, the ring opening of 2H-benzopyrans, 2,4-diphenyland

2,2,4-triphenyl-2H-benzopyran, is found to occur via the excited

singlet state within 2 ps to produce vibrationally excited open forms in the

ground electronic state. In the subnanosecond to submillisecond time

domain, several decay components are observed. These components are

assigned to respective stereoisomers with respect to two double bonds and

one single bond of the open enone forms. As revealed from pump-laser

power dependencies of the yields of the open forms, the photocleavage of

the benzopyran molecules gives at first only the open forms revertible to the

closed form by a single-bond rotation, and the photoexcitation of the first

generated open forms gives rise to other open forms that need a doublebond

rotation for reversion to the original closed form. Such a two-step

two-photon photochromism can be expected to have a wide range of

application.