Wettability characteristics of polyethylene modified with CO2, Nd:YAG, excimer and high-power diode lasers

Interaction of CO2, Nd:YAG, excimer and high-power diode laser (HPDL) radiation with the surface of the biomaterial polyethylene (PE), was found to effect varying degrees of change to the wettability characteristics of the material depending upon the laser used. It was observed that interaction with CO2, Nd:YAG and HPDL effected very little change to the wettability characteristics of the PE. In contrast, interaction of the PE with excimer laser radiation resulted in a marked improvement in the wettability characteristics. After excimer laser treatment, the surface O2 content was found to have increased and the material was seen to be more polar in nature, resulting in a significant increase in the wettability characteristics. The work has shown that the wettability characteristics of the PE could be controlled and/or modified with laser surface treatment. However, a wavelength dependence of the change in the wetting properties could not be deduced from the findings of this work.

In vivo association of lamins with nucleic acids in Drosophila melanogaster

A 32P-labeling strategy was developed to study the interaction(s) in tissue culture cells between proteins and nucleic acids. Interphase and mitotic nuclear lamins were studied in Drosophila Kc cells. After bromodeoxyuridine incorporation and in vivo photo-crosslinking with 366 nm light, it was found that interphase lamins were associated with nucleic acid. Interactions with DNA as well as RNA were detected. In contrast, interaction of nucleic acids with mitotic lamin was not observed. Photo-crosslinking in the presence of antibiotics distamycin and/or chromomycin suggested that interphase lamins interacted with both A-T-rich DNA and G-C-rich DNA; interactions with G-C-rich DNA predominated. These results have implications for understanding the interphase organization of the higher eukaryotic cell nucleus as well as the transition of cells from interphase to mitosis. A model of nuclear organization, consistent with our results, is proposed.

Structural changes in mitochondria induced by uncoupling reagents. The response to proteolytic enzymes

Interaction of uncoupling reagents with bovine serum albumin markedly inhibited its hydrolysis by proteolytic enzymes. The inhibition presumably is due to conformational transitions in the protein substrate induced by the binding of the ligand–uncoupling reagents. The proteolysis of casein, a protein that does not bind these reagents, was not affected, indicating that the proteinases themselves were not inactivated. In contrast, interaction of uncoupling reagents with freshly isolated rat liver mitochondria enhanced their susceptibility to proteolytic enzymes. This was shown by an increase in the release of ninhydrin-reacting material, by an increase in free acid groups and by a decrease in the turbidity of the mitochondrial suspensions. These effects, although opposite in direction to those obtained with albumin, are also presumed to indicate structural changes in the mitochondrial proteins and a disorganization of the protein–phospholipid complex. It is suggested that such structural alterations are expressed functionally as the uncoupling of oxidative phosphorylation.