Energy transfer in lipid bilayers.

The quenching of fluorescence due to energy transfer between a dilute, random array of donor and acceptor chromophores in lipid bilayer was measured and compared to theoretical expressions developed to predict the decrease in emission intensity under these circumstances. The observed intensity was found to be the same function of quencher concentration in both planar, multilamellar dispersions and small, spherical vesicles. The degree of quenching was accurately predicted by a simple relation derived in this paper, as well as a more complex equation previously developed by Tweet, et al. The results suggest that significant quenching may be observed even when the average donor-acceptor separation exceeds the F?rster critical distance by severalfold. Application of these results to problems of current interest in membrane research are discussed.     

Involvement of alpha-2-macroglobulin receptor in clearance of interleukin 8-alpha-2-macroglobulin complexes by human alveolar macrophages

The purpose of this study was to determine if interleukin 8 (IL-8) in complex with alpha2-macroglobulin (alpha-2-M) can be taken up by human alveolar macrophages. First, we demonstrated that human alveolar macrophages have receptors for alpha-2-M but not IL-8. The binding of(125)I-labeled alpha-2-M to the cells was specific and saturable, whereas(125)I-labeled recombinant human IL-8 (rhIL-8) did not bind to macrophages. However,(125)I-rhIL-8-alpha-2-M complexes bound to macrophages, and unlabeled alpha-2-M competed for the binding. We then cultured the cells in the presence of(125)I-rhIL-8-alpha-2-M complexes,(125)I-rhIL-8 alone or buffer for 24 h. Macrophages were lysed, and the released radioactivity measured. IL-8 concentrations in supernatants and cells were also measured using an IL-8 ELISA. When the macrophages were incubated with(125)I-rhIL-8-alpha-2-M complexes there was a significant amount of IL-8 associated with the cells. However, this was not the case when the cells were incubated with(125)I- rhIL-8 alone suggesting that only these complexes were taken-up by human alveolar macrophages. Furthermore, the clearance of complexes was specifically inhibited by a monoclonal antibody against the 515-kDa subunit of the alpha-2-M receptor (alpha-2-MR) but not by an isotopic mouse IgG1. The study shows an important clearance mechanism for IL-8 in the lung.     

Transient Raman study of horseradish peroxidase. Evidence for a lack of extensive heme pocket relaxation subsequent to carbon monoxide photolysis

Time-resolved resonance Raman spectroscopy is a valuable tool for the study of the dynamics of heme-protein interactions. In particular, the photolysis of a ligand by short laser pulses allows for the examination of the dynamic evolution of heme-protein interactions subsequent to ligand dissociation. To date, such studies have been confined largely to hemoglobins and myoglobins. Here we present the results of the first transient Raman study of a peroxidase. Resonance Raman spectra of horseradish peroxidase were obtained within 10 ns of ligand (CO) photolysis at a variety of pH values. We find that there is only minimal relaxation of the heme pocket of horseradish peroxidase in response to ligand photolysis. This relaxation is pH-dependent and most probably involves the heme vinyl substituents. Such behavior is in sharp contrast to the transient behavior of most hemoglobins and beef heart cytochrome oxidase.     

Evidence for the Occurrence of Specific Iron (III)-Binding Compounds in Near-Shore Marine Ecosystems

Aqueous extracts of samples from representative types of near-shore marine ecosystems were examined for growth-promoting activity for the siderochrome auxotroph, Arthrobacter JG-9. Blue-green algal mat and sea grass samples gave strongly positive responses. Relative to Desferal (Ciba Pharmaceutical Co., Summit, N.J.), concentrations up to 110 ng/g (wet weight) of sample were found. In contrast, extracts of anaerobic muds or macroalgae gave no detectable activity. The hydroxamate type of iron chelator may be important in providing a form of iron in sea water readily utilized by the microalgae and marine higher plants.     

BoHV-4-Based Vector Single Heterologous Antigen Delivery Protects STAT1(-/-) Mice from Monkeypoxvirus Lethal Challenge

Monkeypox virus (MPXV) is the etiological agent of human (MPX). It is an emerging orthopoxvirus zoonosis in the tropical rain forest of Africa and is endemic in the Congo-basin and sporadic in West Africa; it remains a tropical neglected disease of persons in impoverished rural areas. Interaction of the human population with wildlife increases human infection with MPX virus (MPXV), and infection from human to human is possible. Smallpox vaccination provides good cross-protection against MPX; however, the vaccination campaign ended in Africa in 1980, meaning that a large proportion of the population is currently unprotected against MPXV infection. Disease control hinges on deterring zoonotic exposure to the virus and, barring that, interrupting person-to-person spread. However, there are no FDA-approved therapies against MPX, and current vaccines are limited due to safety concerns. For this reason, new studies on pathogenesis, prophylaxis and therapeutics are still of great interest, not only for the scientific community but also for the governments concerned that MPXV could be used as a bioterror agent. In the present study, a new vaccination strategy approach based on three recombinant bovine herpesvirus 4 (BoHV-4) vectors, each expressing different MPXV glycoproteins, A29L, M1R and B6R were investigated in terms of protection from a lethal MPXV challenge in STAT1 knockout mice. BoHV-4-A-CMV-A29LgD₁₀₆ΔTK, BoHV-4-A-EF1α-M1RgD₁₀₆ΔTK and BoHV-4-A-EF1α-B6RgD₁₀₆ΔTK were successfully constructed by recombineering, and their capacity to express their transgene was demonstrated. A small challenge study was performed, and all three recombinant BoHV-4 appeared safe (no weight-loss or obvious adverse events) following intraperitoneal administration. Further, BoHV-4-A-EF1α-M1RgD₁₀₆ΔTK alone or in combination with BoHV-4-A-CMV-A29LgD₁₀₆ΔTK and BoHV-4-A-EF1α-B6RgD₁₀₆ΔTK, was shown to be able to protect, 100% alone and 80% in combination, STAT1^(-/-) mice against mortality and morbidity. This work demonstrated the efficacy of BoHV-4 based vectors and the use of BoHV-4 as a vaccine-vector platform.     

Sphingolipid long chain base phosphates can regulate apoptotic-like programmed cell death in plants

Sphingolipids are ubiquitous components of eukaryotic cells and sphingolipid metabolites, such as the long chain base phosphate (LCB-P), sphingosine 1 phosphate (S1P) and ceramide (Cer) are important regulators of apoptosis in animal cells. This study evaluated the role of LCB-Ps in regulating apoptotic-like programmed cell death (AL-PCD) in plant cells using commercially available S1P as a tool. Arabidopsis cell cultures were exposed to a diverse array of cell death-inducing treatments (including Cer) in the presence of S1P. Rates of AL-PCD and cell survival were recorded using vital stains and morphological markers of AL-PCD. Internal LCB-P levels were altered in suspension cultured cells using inhibitors of sphingosine kinase and changes in rates of death in response to heat stress were evaluated. S1P reduced AL-PCD and promoted cell survival in cells subjected to a range of stresses. Treatments with inhibitors of sphingosine kinase lowered the temperature which induced maximal AL-PCD in cell cultures. The data supports the existence of a sphingolipid rheostat involved in controlling cell fate in Arabidopsis cells and that sphingolipid regulation of cell death may be a shared feature of both animal apoptosis and plant AL-PCD.