OBPR Research Updates

Growth characteristics of synchronous human, mouse and bacterial cell cultures produced with a new minimally-disturbing technology were compared to each other and to synchronous bacteria. Based on measurements of cell concentrations during synchronous growth, synchrony persisted in similar fashion for all cells. Cell size and DNA distributions in the mammalian cultures also progressed synchronously and reproducibly for multiple cell cycles. The results demonstrate that unambiguous multi-cycle synchrony, critical for verifying the absence of significant growth imbalances induced by the synchronization procedure, is feasible with these cell lines, and possibly others. Helmstetter CE, Thornton M, Romero A, Eward LK; Department of Biological Sciences, Florida Institute of Technology, Melbourne, FL 32901, USA.

These results along with the cover photo are reported in Cell Cycle, Vol: 2, Issue: 1, pgs: 42-45, 2003.

Fluid Physics PI Michael Soloman (University of Michigan) and his team directly visualize and quantify the local spatial structure of dense colloidal gels of varying volume fraction formed by short-range attractive interparticle interactions by means of confocal laser scanning microscopy. They find that the short-range structure of the gels is similar to that of dense amorphous hard-sphere systems. However, the long-range structure is characterized by voids and density correlations that differ remarkably from amorphous hard spheres and glasses formed through repulsive interactions. Quantification of the volume fraction dependence of the gel isothermal compressibility and Voronoi volume distribution establishes that long-range structural heterogeneity is a distinguishing feature of the static structure of dense colloidal gels formed by short-range attractions.

These results along with the cover photo are reported in Langmuir, Vol. 19, Issue 3, pp 509 - 512, 2003.

Cover Caption: "Cover illustration by P. Varadan. The left-hand cover image is a two-dimensional (2D) slice of a 3D image volume of a colloidal particle gel acquired by confocal laser scanning microscopy (CLSM). The particles, which have a fluorescent core, a nonfluorescent shell, and an organophilic surface coating, are 832 nm in diameter. The colloids gel due to short-range attractive interparticle forces when they are dispersed in hexadecane at the colloid volume fraction shown (26%). The right-hand image shows in 2D projection the 3D coordinates of particles in the gel, as determined by quantitative image processing. Structural measures such as the radial distribution function and void volume distributions can be computed from the coordinates just as for the results of a computer simulation. The images demonstrate that these materials, which are models of suspensions that are ultimately processed into monolithic ceramics and membranes, exhibit long-range void structure that is strikingly heterogeneous. 3D visualization by CLSM provides new possibilities for the elucidation of structure in submicrometer colloidal suspensions. For more information see "Direct Visualization of Long-Range Heterogeneous Structure in Dense Colloidal Gels", by Priya Varadan and Michael J. Solomon on pages 509-512 of this issue. Copyright 2003 American Chemical Society."