Physics of transport and traffic phenomena in biology: from molecular motors and cells to organisms

Traffic-like collective movements are observed at almost all levels of biological Systems. Molecular motor proteins like, for example, kinesin and dynein, which are the vehicles of almost all intra-cellular transport in eukaryotic cells, sometimes encounter traffic jam that manifests its a disease of the organism. Similarly, traffic jam of collagenase MMP-1, which moves on the collagen fibrils of the extracellular matrix of vertebrates, has also been observed in recent experiments. Novel efforts have been made to utilize some uni-cellular organisms as "micro-transporters". Traffic-like movements of social insects like ants and termites on trails are, perhaps, more familiar in our everyday life. Experimental, theoretical and computational investigations in the last few years have led to a deeper understanding of the generic or common physical principles involved in these phenomena. In this review we critically examine the current status of our understanding. expose the limitations of the existing methods, mention open challenging questions and speculate on the possible future directions of research in this interdisciplinary area where physics meets not only chemistry and biology but also (nano-)technology. (C) 2005 Elsevier B.V. All rights reserved.