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Biomedical subjects

H De Silva

Publications and source records attributed to H De Silva.

4 recordsLinked to original sources
PubMed1999

Unidirectional rotary motion in a molecular system.

The conversion of energy into controlled motion plays an important role in both man-made devices and biological systems. The principles of operation of conventional motors are well established, but the molecular processes used by 'biological motors' such as muscle fibres, flagella and cilia to convert chemical energy into co-ordinated movement remain poorly understood. Although 'brownian ratchets' are known to permit thermally activated motion in one direction only, the concept of channelling random thermal energy into controlled motion has not yet been extended to the molecular level. Here we describe a molecule that uses chemical energy to activate and bias a thermally induced isomerization reaction, and thereby achieve unidirectional intramolecular rotary motion. The motion consists of a 120 degrees rotation around a single bond connecting a three-bladed subunit to the bulky remainder of the molecule, and unidirectional motion is achieved by reversibly introducing a tether between the two units to energetically favour one of the two possible rotation directions. Although our system does not achieve continuous and fast rotation, the design principles that we have used may prove relevant for a better understanding of biological and synthetic molecular motors producing unidirectional rotary motion.

Models, Molecular↗
PubMed1998

Identification of a novel stress activated kinase in kidney and heart.

We have previously described the patterns of stress kinase activation in rat kidney and heart in response to ischemia/reperfusion (Yin et al., 1997, J. Biol. Chem. 272, 19943-19950). During the course of these studies, we observed the activation of a novel kinase capable of phosphorylating c-Jun on serines 63 and 73. The molecular weight of this kinase is approximately 37 kD, significantly below the molecular weight of all previously identified Jun N-terminal kinase (JNK) isoforms. The pattern of activation of this 37 kD kinase in response to ischemia/reperfusion in both kidney and heart is distinct from that of known JNK isoforms. Western analysis of human renal proximal tubular epithelial (RPTE) cells, using a non-isoform specific phospho-JNK antibody, revealed the phosphorylation (activation) of a 37 kD protein in response to hypoxia. The 37 kD protein in RPTE cells is phosphorylated by other stress stimuli capable of activating JNK. Western analysis of tissues, using a non-isoform specific JNK antibody, identifies a cross-reactive 37 kD protein expressed in the liver, thymus and lymph node which is likely to correspond to the 37 kDa stress-activated kinase. The results of this study have led to the identification of a potentially novel kinase closely related to JNK but showing a distinct pattern of activation.

Animals↗