New Opportunities in Synchrotron X-ray Crystallography

High-pressure crystallography

Since the late 1950's, high-pressure structural studies have become increasingly frequent, following the inception of opposed-anvil cells, development of efficient diffractometric equipment (brighter radiation sources both in laboratories and in synchrotron facilities, highly efficient area detectors) and procedures (for crystal mounting, centring, pressure calibration, collecting and correcting data). Consequently, during the last decades, high-pressure crystallography has evolved into a powerful technique which can be routinely applied in laboratories and dedicated synchrotron and neutron facilities. The variation of pressure adds a new thermodynamic dimension to crystal-structure analyses, and extends the understanding of the solid state and materials in general. New areas of thermodynamic exploration of phase diagrams, polymorphism, transformations between different phases and cohesion forces, structure-property relations, and a deeper understanding of matter at the atomic scale in general are accessible with the high-pressure techniques in hand. A brief history, guidelines and requirements for performing high-pressure structural studies are outlined.

Synchrotron X-ray studies of lipids and membranes: a critique

This review gives a description of techniques, suitable for the study of lipid dispersions and unorientated membranes, that are available at synchrotron facilities to determine either the kinetics of transitional phenomena in the time after a temperature or pressure jump is initiated, or the phases present while a sample undergoes a phase transition. Included in this description is information about synchrotron X-ray sources, sample holders and temperature controllers, detection systems, as well as data reduction. Examples involving lipid dispersions are provided to illustrate the application of these methods using synchrotron radiation.

Advances in molecular biology. Potential impact on diagnosis and treatment of disorders of the thyroid

Advances in molecular biology research continue to have a major impact on clinical medicine. These advances have provided a means to produce proteins previously available in limited supply and allow for the production of novel proteins that are improved agonists or else antagonists with greater specificity for therapeutic targets. Newer drug delivery systems should facilitate delivery of these proteins. By combining the capabilities to produce drug targets in acceptable quantities with improved methods for determining the three-dimensional structures of these targets, novel organic therapeutic molecules that act on these targets will be designed. Gene transfer therapy using genes that express important proteins or that encode "antisense" RNAs that inhibit the translation of specific mRNAs will soon become a reality. The use of RFLPs and PCR methodologies promises increased means to diagnose specific genetic diseases and infections. Most importantly, molecular biology is helping to understand the mechanisms of disease such that novel diagnostic and therapeutic approaches can be described. These advances are providing an understanding of the mechanisms involved in cancers of the thyroid gland. They have already led to an enhanced understanding of (1) the growth factors that control proliferation of the thyroid gland, (2) the potential steps in thyroid nodule and neoplasia development, (3) particular mutations that may occur as thyroid cancers develop, (4) oncogenes that are expressed in thyroid cancers, and (5) the genetic defects that are responsible for thyroid gland malignancies in the multiple endocrine neoplasia (MEN) syndromes. With the latter, the RFLP technology has already provided an enhanced means to diagnose the disorder. With further progress, enhanced means for diagnosis and treatment should emerge. Molecular biology techniques are contributing to an increased understanding of the mechanisms of development of autoimmune thyroid disease as with Graves' disease and Hashimoto's thyroiditis. The potential role of infections, histocompatibility antigens, thyroid gland and extraglandular antigens, immune modulators, subpopulations of T-cells such as suppressor and helper cells, other cells involved in immune responses, and a combination of influences of several different functions on the thyroid gland are being defined. This knowledge should soon suggest improved means for diagnosis and treatment. Understanding of the function of the thyroid hormone receptors should have clinical importance. This knowledge suggests a means to develop thyroid hormone antagonists that may be used to more rapidly ameliorate the effects of hyperthyroidism and could be useful in nonthyroidal disorders such as cardiac arrhythmias.(ABSTRACT TRUNCATED AT 400 WORDS)