Science Progress (2004), 87 (1)

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Compatible and counteracting

solutes: protecting cells from the

Dead Sea to the deep sea

PAUL H. YANCEY

Cells of many organisms accumulate certain small organic molecules –

called compatible and counteracting solutes, compensatory solutes, or

chemical chaperones – in response to certain physical stresses. These

solutes include certain carbohydrates, amino acids, methylamine and

methylsulphonium zwitterions, and urea. In osmotic dehydrating stress,

these solutes serve as cellular osmolytes. Unlike common salt ions and urea

(which inhibit proteins), some organic osmolytes are compatible; i.e., they

do not perturb macromolecules such as proteins. In addition, some may

protect cells through metabolic processes such as antioxidation reactions

and sulphide detoxification. Other osmolytes, and identical or similar

solutes accumulated in anhydrobiotic, heat and pressure stresses, are

termed counteracting solutes or chemical chaperones because they stabilise

proteins and counteract protein-destabilising factors such as urea,

temperature, salt, and hydrostatic pressure. Stabilisation of proteins, not

necessarily beneficial in the absence of a perturbant, may result indirectly

from effects on water structure. Osmotic shrinkage of cells activates genes

for chaperone proteins and osmolytes by mechanisms still being elucidated.

These solutes have applications in agriculture, medicine and biotechnology.

Keywords: osmolyte, antioxidant, pressure, urea, trimethylamine

oxide, temperature, compatible, counteracting, compensatory,

chaperone

Near-field optics and

spectroscopy for molecular

nano-imaging

SATOSHI KAWATA,1,3 YASUSHI INOUYE 2,3 AND

TARO ICHIMURA2

Application of near-field optical microscopy with a sharp metallic probe to

Raman spectroscopy brings microanalysis of materials to their nanoidentification

and imaging. The local plasmon polariton excitation on the

probe tip results in the localization and amplification of the optical field at

the vicinity of the tip. The tip-enhanced near-field Raman spectroscopy has

analyzed DNA base molecules and single-walled carbon nanotubes

(SWNTs) with the nanometric spatial resolution and sufficient sensitivity.

Combined with tip pressurization and nonlinear effects, the tip-enhanced

near-field Raman spectroscopy gives additional spectral information or

improves the spatial resolution and sensitivity. This article introduces the

recent progresses on the tip-enhanced near-field Raman spectroscopy and

imaging.

Keywords: near-field optics, molecular nano-imaaging

Superconductivity

F. M. GROSCHE

Electrons in metals can self-organise. The complex interplay between lattice

dynamics, electrostatic interaction and band structure brings forth numerous

types of electronic order. Because of its spectacular phenomenology,

superconductivity has enjoyed a central place among these, since its discovery

nearly 100 years ago. This short introduction into one of the largest

fields of condensed matter research focuses on the most fundamental

experimental signatures of superconductivity – perfect conductivity and

perfect diamagnetism – and their explanation. A conventional broken symmetry

argument is presented, which introduces a superconducting order

parameter in analogy to the case of superfluid 4He, and discusses its microscopic

origin in the framework of the BCS model of superconductivity. New

materials have brought to light novel forms of superconductivity. Many

cases are now known which fall outside the orthodox BCS model, ranging

from the high temperature superconductors, to various organic and d- and

f- metal compounds. The article presents key concepts from this intense

area of research and touches on the equally puzzling behaviour of many of

these materials above their superconducting transition temperature.

Keywords: Superconductivity, superfluidity, broken symmetry