Virucidal activity of retinal

Herpes simplex virus type 2 and simian virus 40 were rapidly inactivated by retinal at micromolar concentrations. Other fat-soluble vitamins, particularly vitamin A derivatives, were also active against herpes simplex virus type 2 and several lipid-containing bacteriophages.

Extreme sensitivity of enveloped viruses, including herpes simplex, to long-chain unsaturated monoglycerides and alcohols

Unsaturated monoglycerides and alcohols of chain lengths of 16 or 18 carbons were found to be extremely potent inactivators of two enveloped viruses, herpes simplex virus type 2 and bacteriophage phi6. The lipid-containing bacteriophage PM2 was also inactivated by some of these amphiphilic molecules. Treatment of herpes simplex virus type 2 with these compounds at concentrations as low as 0.2 muM reduced virus survival to 50% in 30 min, making these agents the most potent inactivators of herpes simplex viruses discovered that are not cytotoxic to mammalian cells. Detailed characterizations of the effects of unsaturated monoglycerides and alcohols on bacteriophages phi6 and PM2 showed that the inactivated phi6 virion remained nearly intact but that PM2 was almost completely disrupted by the inactivating treatment. Some of the compounds inactivate the viruses even at low temperature (0 degrees C). Excess amounts of diglycerides and phospholipids interfere with the inactivating abilities of some of the unsaturated monoglycerides and alcohols against phi6 and PM2. Our findings suggest that the unsaturated monoglycerides and some of the unsaturated alcohols should be further studied as potential antiviral agents, particularly for application to herpesvirus-infected areas of the skin and accessible epithelium.

A fluorescence enhancement assay of cell fusion

Two probes were synthesized which consist of fluorescent molecules conjugated to saturated hydrocarbon chains, 18 carbons long, to ensure their localization into cellular membranes. There is an overlap between the emission spectrum of one probe (donor) and the absorption spectrum of the other probe (acceptor). By the use of appropriate wavelengths it is possible to specifically excite the donor probe and record the fluorescence of the acceptor probe. Two cell populations, each labelled with one of the probes, were infected with a virus that causes cell fusion, mixed in equal proportions, and the fluorescence of the acceptor probe measured as a function of time after infection. An increase in fluorescence was observed beginning at the time of onset of cell fusion indicating a mixing of the fluorescent membrane molecules. An investigation of the distance dependence indicated that the increase in fluorescence was mainly due to resonance energy transfer and not to photon emission and reabsorption. Resonance energy transfer requires that the 2 probes be close together and that there be an overlap of the emission spectrum of the donor probe and the absorption spectrum of the acceptor probe. The possible application of this assay to other types of membrane fusion is noted.

Factors restricting diffusion of water-soluble spin labels

Line broadening of spin label signals is treated in terms of concentration, viscosity, charge and temperature dependencies. Line broadening of spin label signals may be caused either by spin label interactions or by the interaction between a spin label and a second paramagnetic species. Line broadening has been related to collision frequency in the literature and is treated in that way here. Collision frequency is related to diffusion processes in a way that allows information to be obtained about the diffusion environment. Several potential spin label line-broadening agents are compared as to their effectiveness. Small polymer beads with graduated pore sizes are used to show that collisional broadening has a marked dependence on the long-range structure of the diffusion environment. Application of these results to biological diffusion processes is considered.

Inositol-less death in yeast results in a simultaneous increase in intracellular viscosity

Inositol auxotrophs of yeast developing on isositol-deficient medium continue protein synthesis for 4-6 h, lose viability rapidly after 6 h, and show an increase in cytoplasmic viscosity as measured by spin label rotational motion. Cycloheximide prevents the rapid loss of cell viability, stops protein synthesis, and simultaneously prevents an increase in cytoplasmic viscosity. From these observations, we infer that intracellular translational diffusion is upset as a consequence of inositol starvation. Cell death may be caused by a modified intracellular diffusion environment.

Spin-label studies on the aqueous regions of phospholipid multilayers

Water-soluble spin labels were used to study dimyristoyllecithin (DML) phospholipid multilayers. Previous studies report that there is a "bound" water region associated with dimyristoyllecithin containing about 10 molecules of water per phospholipid, a "trapped" water region located between the lamellae containing approximately 11 molecules per phospholipid, and a "ftion show that certain water-soluble spin-label mol-cules have their motional properties differentially modified by these three water environements. Furthermore, the labels also reveal the onset of lipid-phase transitions even though they have high water solubility. A phosphate-containing spin label demonstrated strong an isotropic motion in the lipid-water system above the phase transition but not below. The addition of cholesterol to the DML-water system removed the anisotropic motion of 2,2,6,6-tetramehtyl-4-phosphopiperidine-N-oxyl (Tempophosphate) and obscured the detection bound, trapped, and free water. In addition to the change-charge interactions between Tempophosphate and DML, two other spin labels were used both in the charged and uncharged states. 2,2,6,6-Tetramethyl-4-aminopiperidine-N-oxyl (Tempamine) in the charged state showed extremely strong anisotropic motion, presumably due to the interaction between the charged amine and the phosphate group of DML. When only partially charged, Tempamine showed much less anisotropic motion. PCA was analyzed at pH values where the carboxyl group was protonated and unprotonated. The resulting interaction was different at the two pH values. These water-soluble spin labels mimic ionic or nonionic solutes. Upon freezing, the spin labels are shown to be expelled from the ice regions into the remaining aqueous regions. The usefulness of this approach in studying solute behavior when freezing occurs and potential studies involving aqueous regions of cytoplasm are considered.

Inactivation of lipid-containing viruses by long-chain alcohols

This report describes the inactivation of lipid-containing viruses by several long-chain alcohols. A striking peak in antiviral activity was found for saturated alcohols having chain lengths from 10 to 14 carbons. Viruses having different membrane structure showed different susceptibilities to alcohols having different chain lengths and structural features. Decanol, dodecanol, and tetradecanol readily inactivated herpes simplex virus and the enveloped bacterial virus phi6. The lipid-containing virus PM2 was susceptible to decanol and dodecanol but comparatively unsusceptible to tetradecanol. The branched-chain alcohol phytol, a naturally occurring component of chlorophyll, was active against phi6 and herpes simplex virus but not against PM2. Polyoma virus and the bacteriophage phi23-1-a, which do not contain lipids, were not susceptible to inactivation by any of the alcohols tested. Experiments were also carried out to determine the effects of these compounds on cells. At 0.5 mM, decanol lysed human embryonic lung cells, erythrocytes, and the bacterial hosts for phi6 and PM2. Dodecanol, tetradecanol, and phytol at this concentration were less damaging to cells. At 0.05 mM, none of the alcohols caused observable cytopathic effects on human embryonic lung cells, although several of the alcohols at this concentration were active against herpes simplex virus. Our findings suggest that dodecanol, tetradecanol, and phytol may warrant further studies as potential antiviral agents, particularly for topical application to virus-infected areas of the skin.

Inactivation of the enveloped bacteriophage phi6 by butylated hydroxytoluene and butylated hydroxyanisole

Butylated hydroxytoluene (BHT) is a potent inactivator of the enveloped bacterial virus ø6 at concentrations as low as 3 x 10(-5) M. The viral envelope is not removed by BHT treatment, in contrast to the effects of exposure to the detergent Triton X-100. BHT-treated viruses are morphologically indistinguishable from controls but are defective in their ability to attach to the host cell. Temperature at the time of exposure was found to be a crucial factor in the effectiveness of BHT against ø6. A precipitous drop in the degree of inactivation by 3 x 10(-5) M BHT occurred when the temperature was lowered from 20 to 15 C. Calcium ions were found to potentiate the effect of BHT, particularly at lower temperatures where BHT alone was relatively ineffective. Barium and strontium, but not magnesium, were also effective in enhancing the activity of BHT. A structurally related molecule, butylated hydroxyanisole (BHA), was also found to inactivate ø6 virus, but higher concentrations were required than with BHT. Both BHT and BHA are commonly used as food additives, have apparent low toxicity to humans and other animals, and are potentially useful as antiviral agents.

Changes in the restriction of molecular rotational diffusion of water-soluble spin labels during fatty acid starvation of yeast

Yeast mutants lacking fatty acid synthetase activity (fas-) die when deprived of saturated fatty acid under conditions which are otherwise growth-supporting. The spin label technique is used to show that restriction of molecular rotational diffusion of spin label molecules dissolved in aqueous zones increases several fold under conditions of fatty acid starvation while the apparent physical state of cellular hydrocarbon zones remains essentially unchanged. We focus attention on the cellular aqueous interior as the potential site of alteration under selective starvation conditions. Correspondences exist between restriction of molecular motion of water soluble spin labels dissolved in the cell and loss of cell viability. The correspondences to changes in the molecular motion of hydrocarbon soluble spin labels are much less or are not detectable.

Inactivation of the lipid-containing bacteriophage PM2 by butylate hydroxytoluene

Several factors have been investigated which are of significance in the inactivation of PM2, a lipid-containing bacterial virus, by butylated hydroxytoluene (BHT). Studies of the time dependence of inactivation during exposure to BHT showed that virus killing occurs rapidly, with the majority of the effect taking place in the first 5 min. The degree of inactivation is dependent upon the initial virus titer, the solvent from which BHT is added, and the presence of a variety of protective agents, including surfactants, bovine serum albumin, and bacterial cells. Sucrose gradient analysis of (32)P-labeled, BHT-treated virus was used to determine the degree to which the virion is disrupted by BHT. These experiments show that the (32)P-labeled molecules are converted into very slowly sedimentable material by BHT treatment, indicating complete destruction of the virus particle.

Spin label evidence for the role of lysoglycerophosphatides in cellular membranes of hibernating mammals

The phospholipid composition of ground squirrel heart muscle changes during hibernation: more lysoglycerophosphatides are found in the hibernating state than in the active state. Phase transitions inferred from spin label motion occur in the usual manner typical of mammalian mitochondria for the mitochondria and mitochondrial lipids from active squirrels. However, a conspicuous absence of a spin label-detectable phase transition is observed in equivalent preparations from hibernating animals. The addition of lysolecithin to preparations from active squirrels removes the break and induces a straight line in the Arrhenius plot. The lack of a spin label-detectable phase transition in hibernating animals, therefore, is attributed to an increased content of lysoglycerophosphatides present in the phospholipids during hibernation.

Effect of lipid alkyl chain perturbations on the assembly of bacteriophage PM2

The lipid-containing bacteriophage PM2 can produce infectious virus in cultures infected at temperatures up to 31.5 degrees C, but not at 34 degrees C. Its host, Pseudomonas BAL-31, grows at 34 degrees C and cultures infected at that temperature undergo lysis. Sucrose-gradient analysis shows that 34 degrees C lysates contain no PM2-like particles. Temperature-shift experiments establish that the thermally sensitive process is late in infection when virus assembly is taking place. Adamantanone, a small hydrophobic molecule that perturbs membrane hydrocarbon zones, prevents the production of infective virus. Concentrations which prevent virus production have no effect on host-cell growth or stability of mature virions. Adamantanone exerts its effects late in the infectious cycle, and lysates amde in its presence contain no PM2-like particles. These experiments, carried out at 25 degrees C, indicate that adamantanone prevents the assembly of stable PM2 virus. Spin-label studies suggest that the lipid alkyl chains of the host-cell membrane are in an "ordered" state at temperatures below about 33 degrees C and undergo a transition to a "disordered" state above that temperature. Furthermore, the addition of adamantanone perturbs the hydrocarbon zones, producing a greater degree of disorder even below 25 degrees C. Our findings suggest that the cell membrane can function and grow with the lipid alkyl chains in either the "ordered" or "disordered" state, but that the "ordered" state must be maintanined for PM2 assembly to occur.

Butylated hydroxytoluene inactivated lipid-containing viruses

Butylated hydroxytoluene (BHT) is widely used as a food preservative for its antioxidizing property. This small, hydrophobic molecule has been found to be a potent inactivator of lipid-containing mammalian and bacterial viruses.

Ultraviolet mutagenesis and its repair in an Escherichia coli strain containing a nonsense codon

Ultraviolet mutagenesis and its repair were studied mainly in WU36-10-89, a uvr(-) strain of Escherichia coli containing a UAG mutation in a gene for leucine biosynthesis. Following ultraviolet (UV) irradiation revertants appearing with or without direct photoreactivation (PR) were classified according to the presence and type of suppressor they contained. We find UV mutation production to be quite specific. An analysis of revertants produced by UV indicates they are formed mainly from GC --> AT and that the miscoding is due to a cytosine residue at the site of mutation in a cytosine-thymine (CT) dimer. We propose that the dimer serves as template during some aspects of repair replication and at the time of replication the C in the dimer directs the insertion of A in the complementary strand. We also note that C --> A and T -->G changes caused by a CT dimer occur much less frequently.