Attempts to fabricate mechanical devices on the molecular level have yielded analogues of rotors, gears, switches, shuttles, turnstiles and ratchets. Molecular motors, however, have not yet been made, even though they are common in biological systems. Rotary motion as such has been induced in interlocked systems and directly visualized for single molecules, but the controlled conversion of energy into unidirectional rotary motion has remained difficult to achieve. Here we report repetitive, monodirectional rotation around a central carbon-carbon double bond in a chiral, helical alkene, with each 360 degrees rotation involving four discrete isomerization steps activated by ultraviolet light or a change in the temperature of the system. We find that axial chirality and the presence of two chiral centres are essential for the observed monodirectional behaviour of the molecular motor. Two light-induced cis-trans isomerizations are each associated with a 180 degrees rotation around the carbon-carbon double bond and are each followed by thermally controlled helicity inversions, which effectively block reverse rotation and thus ensure that the four individual steps add up to one full rotation in one direction only. As the energy barriers of the helicity inversion steps can be adjusted by structural modifications, chiral alkenes based on our system may find use as basic components for 'molecular machinery' driven by light.

The interleukin-2 (IL-2) receptor gamma chain (IL-2R gamma) is an essential component of high- and intermediate-affinity IL-2 receptors. IL-2R gamma was demonstrated to be a component of the IL-4 receptor on the basis of chemical cross-linking data, the ability of IL-2R gamma to augment IL-4 binding affinity, and the requirement for IL-2R gamma in IL-4-mediated phosphorylation of insulin receptor substrate-1. The observation that IL-2R gamma is a functional component of the IL-4 receptor, together with the finding that IL-2R gamma associates with the IL-7 receptor, begins to elucidate why deficiency of this common gamma chain (gamma c) has a profound effect on lymphoid function and development, as seen in X-linked severe combined immunodeficiency.

Interleukin‐3 (IL‐3) is an important regulator of hemopoiesis and considerable effort has been directed towards the study of its mechanism of signal transduction. In this paper, we describe the first molecular identification of a STAT transcription factor that is activated by IL‐3. STATs exist in a cytoplasmic, transcriptionally inactive form which, in response to extracellular signals, become tyrosine phosphorylated and translocate to the nucleus where they bind to specific DNA elements. Several of these DNA elements were found which bind proteins in an IL‐3‐responsive manner. Analysis of these bandshift complexes with available antibodies to the known STATs suggests that IL‐3 activates the DNA‐binding ability of STAT5, a protein which was originally characterized as a prolactin‐responsive transcription factor in sheep. IL‐5 and granulocyte‐macrophage colony stimulating factor (GM‐CSF), which share a common signaling receptor subunit with IL‐3, also activate STAT5. Unexpectedly, two murine STAT5 homologs, 96% identical to each other at the amino acid level, were isolated and IL‐3‐dependent GAS binding could be reconstituted in COS cells transfected with IL‐3 receptor and either STAT5 cDNA. In IL‐3‐dependent hemopoietic cells, both forms of STAT5 are expressed and activated in response to IL‐3.

To determine the absolute configuration of chiral compounds, theoretical calculations of ECD spectra have been extensively carried out, where the shape of component CD Cotton effects was approximated by the Gaussian distribution curve. However, in some articles, errors are found in the equations of Gaussian curve expressing CD Cotton effects. In this short review, the correct and general forms of the Gaussian equation and the approximation of the CD curve by other methods are described.

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