A new material concept for the red cell membrane

The proposition is made that the red cell membrane is a two-dimensional, incompressible material and a general stress-strain law is developed for finite deformations. In the linear form, the character of such a material is analogous to a two-dimensional Mooney material (e.g., rubber), indicating that the molecular structure in the plane of the membrane would consist of long chains, randomly kinked and cross-linked in the natural state. The loose network could be provided by the protein component and the lipid phase could exist interstitially as a liquid bilayer, giving the membrane its two-dimensional incompressibility. The material provides the capability of large deformations exhibited by the discocyte and yet the rigidity associated with the osmotic spherocyte state. It is demonstrated that a membrane of this type can form a sphere at constant area. An illustrative example of the application to single cell discocyte-to-osmotic spherocyte transformations is presented.

New membrane concept applied to the analysis of fluid shear- and micropipette-deformed red blood cells

A two-dimensional elastomer material concept of the red cell membrane is applied to the analysis of fluid shear-deformed, point-attached red cells and micropipette aspiration of red cell disks. The elastic constant (corresponding to the "shear" modulus multiplied by the membrane thickness) is of the order 10(-2) dyn/cm for both cases. Additional experimental observations are in agreement with the membrane model, e.g. teardrop and "tether" formation of the sheared disks, pressure difference vs. aspirated length of the cell for micropipette experiments, etc

Studies of DNA-infected disrupted cell preparations

Procedures for increasing both sensitivity and reproducibility of virus production in disrupted DNA-infected cell preparations have been described. A variety of chemical agents and physical procedures, including fractionation by centrifugation, were tested for effects on the ability of disrupted cell preparations to form virus particles. DNA prepared from lambda-virulent phage, a deletion mutant derived from lambda-temperate phage, was shown to be infectious in disrupted cell preparations. When infectious lambda-virulent and lambda-temperate phage DNA were added simultaneously to frozen and thawed cell preparations, a marked increase in the production of infectious units was observed. This effect was eliminated when the biological activity of either DNA type was destroyed by heat. Phage particles produced by such mixed infections had the same buoyant density as the respective parental phages.

Protein components of bacteriophages lambda and lambda virulent

Parallel studies have been made of the protein coats of the temperate bacteriophage lambda and of a deletion mutant, lambda virulent. A new method for preparing ghosts of both phages by the action of Cu(++) is described. Protein ghosts of both phages can be dissolved in citrate at pH values below 3, more rapidly in the presence of 8 m urea. Both phages yielded three apparently identical protein components which can be separated by thin-layer gel filtration and thin-layer gel electrophoresis. The protein of molecular weight 47,000 +/- 1,500 represents about 55% of the protein of the ghosts and is therefore likely to be the subunit of the head. The other proteins of molecular weight 30,000 +/- 1,500 and 16,000 +/- 1,500 represent approximately 25% and 20% of the protein, respectively. Amino acid analyses of the ghosts from the two phages have been carried out and show no significant differences. The buoyant density of phage lambda virulent is 0.016 g/ml less than that of lambda. Since no differences have been found in the protein components of the two phages, this indicates that the virulent mutant contains approximately 16% less deoxyribonucleic acid than the temperate phage.

Tritiated thymidine: effect of decomposition by self-radiolysis on specificity as a tracer for DNA synthesis

Tritiated thymidine undergoes decomposition by self-radiolysis. As shown by beta liquid-scintillation measurement and by autoradiography, the resultant breakdown products did not label DNA, but entered macromolecules, other than nucleic acid, contained in the cytoplasm. Caution should be exercised in using aged tritiated thymidine solutions.

Properties of infectious T1 deoxyribonucleic acid

T1 deoxyribonucleic acid (DNA) infection of spheroplasts was characterized by the following. A small number of the DNA molecules initiated infectious centers, and a small number of the spheroplasts were infected by T1 DNA. Once a favorable encounter of T1 DNA with spheroplast occurred, a minimum of 20 to 30 min was required for T1 DNA to enter the spheroplast. The mature T1 particles produced in the infection of spheroplasts by T1 DNA were released in a burst, but the average burst size was quite small compared with a normal burst of the phage-infected bacteria. T1 DNA preparations, capable of causing viral growth in spheroplasts, did not require detectable amounts of protein for infectivity, were homogeneous in band and boundary sedimentation, and had a guanine plus cytosine content of 48% and a minimal molecular weight of 35 x 10(6). Denatured T1 DNA, like denatured lambdaDNA, did not infect spheroplasts. Renatured T1 DNA was not infectious; this was in marked contrast to renatured lambdaDNA.