Detergent NP-40 Research Articles

Identification and characterization of nuclear calmodulin-binding proteins of Saccharomyces cerevisiae

Nuclear calmodulin-binding proteins of the yeast Saccharomyces cerevisiae were investigated. The soluble fractions after serial treatments of the isolated nuclei with buffers containing the nonionic detergent NP-40 (F1), 0.5 M KCl (F2) and 2.0 M KCl (F3) in this order, and the residual proteins (F4) were obtained. The calmodulin-binding proteins of the nucleus and nuclear subfractions were identified using the gel overlay method using 125I-calmodulin. Each subnuclear fraction contained a large number of components that bound calmodulin in a Ca 2+-dependent or -independent manners. The calmodulin-binding proteins were isolated from F1 and F2 subnuclear fractions by affinity chromatography. The affinity-purified proteins bound calmodulin in a Ca 2+-dependent manner when analyzed using the gel overlay method. The major calmodulin-binding components of F1 were 44, 42, 36, 32 and 29 kDa proteins, and those of F2 were 200, 100, 40, 42, 36, 34 and 32 kDa proteins. The isolated proteins also contained several Coomassie-blue stained proteins that did not bind calmodulin and, therefore, may represent the proteins associated with the calmodulin-binding proteins. Antisera raised against the affinity-purified preparation of F1 and F2 recognized almost all of the calmodulin-binding proteins present in the fraction and several other proteins of the nucleus. The presence of Ca 2+-dependent protein phosphatase (type 2B) in the nucleus was demonstrated by Western blotting. The enzyme was localized predominantly in F1 and F4.

Chromatin analysis in yeast using NP-40 permeabilised sphaeroplasts.

Chromatin analysis in yeast using NP-40 permeabilised sphaeroplasts.

Comparison of centrifugation methods for molecular and morphological analysis of membranes associated with RNA replication of the flavivirus Kunjin

Kunjin virus-infected cells were lysed and the cytoplasmic extract was subjected to sedimentation analysis. After centrifugation at 16000 × g for 10 min about 70% of the original RNA-dependent RNA polymerase (RDRP) was recovered in the pellet; most of this enzymic activity was recovered in the soluble fraction after treatment with NP40 detergent. Membrane fractions were prepared from cytoplasmic extracts by centrifugation in discontinuous density gradients comprising w/w or w/v sucrose solutions, either for 3 h (top-loaded on 4 ml 20–60% sucrose) or for 19 h (centre-loaded in 37 ml 0–60% sucrose). Similar separations of bands of light membranes were obtained in all gradients. Multi-layered heavy membrane bands obtained with w/w sucrose gradients were resolved into two well-separated bands (F4 and F5) using w/v sucrose gradients. Thin-section electron microscopy of embedded membrane fractions, gel analysis of intracellular RNA, and RDRP assays showed that the w/w centre loading method and the w/v top-loading (short spin) method produced similar recoveries and distributions of smooth and rough membranes, intact virus particles and RDRP activity. The distribution of intracellular viral RNA and proteins was coincident with the RDRP, all being located in the F4 and F5 bands which contained the characteristic membrane structures induced during flavivirus infection. Significant advantages of the preferred method (w/v sucrose, top loading and short spin) were its rapidity, good preservation of membranes and RDRP, and the concentrations of RDRP achieved in the small volume fractions collected from a total of 4.5 ml.

Extraordinarily low density of hepatitis C virus estimated by sucrose density gradient centrifugation and the polymerase chain reaction.

The genomic RNA of hepatitis C virus (HCV) in the plasma of volunteer blood donors was detected by using the polymerase chain reaction in a fraction of density 1.08 g/ml from sucrose density gradient equilibrium centrifugation. When the fraction was treated with the detergent NP40 and recentrifuged in sucrose, the HCV RNA banded at 1.25 g/ml. Assuming that NP40 removed a lipid-rich surface coat from HCV, the 1.08 g/ml and 1.25 g/ml HCV RNA may correspond to intact HCV virions and nucleocapsids, respectively. The extraordinarily low density of the virion is unusual in comparison to the density of classified viruses.

Isolation of matrix protein M1 from influenza viruses by acid-dependent extraction with nonionic detergent

Influenza viruses were disrupted layer by layer with the nonionic detergent NP-40 at fixed pH. Treatment of the virions with NP-40 at neutral or mildly alkaline pH (6.8-8.0) yielded viral core structures containing M1 protein. The matrix M1 protein was selectively extracted from cores at acidic pH 3.0-4.5 with citrate, acetate, and phosphate buffers or with morpholinoethanesulfonic acid. The resulting M1 protein sedimented in a glycerol gradient with a coefficient of 2.8 S and most likely existed as a monomeric form of the 27,000-Da polypeptide. An antigenic map of the monomeric protein M1 tested with a panel of monoclonal anti-M1 antibodies was found to be similar to those of the assembled M1 protein in whole virions. The isolated M1 protein retained biological properties and inhibited the RNA polymerase activity of viral RNP. This transcription-inhibition function of M1 monomers was specifically restricted by one of the monoclonal antibodies studied.

The characterization of free, cytoskeletal and membrane-bound polysomes in Krebs II ascites and 3T3 cells

Polysomes from Krebs II ascites and 3T3 cells were separated into three populations by using a sequential extraction method. Free polysomes were released by using a combination of low salt (25 mM KCl) and NP-40 detergent in the lysis buffer. The cytoskeletal bound polysomes were subsequently released by raising the salt concentration to 130 mM and finally, polysomes bound to the membranes of the endoplasmic reticulum were extracted by the combined treatment with Triton X-100 and deoxycholate. The results presented here illustrate that the three polysome-containing fractions differ in many parameters such as polysome profiles, cytoskeletal components and phospholipid content. When polyA-containing mRNA was isolated from the three polysome fractions and translated in an in vitro system, some differences were observed in the patterns of proteins being synthesized.

Modified subcellular localization of interferon-induced p68 kinase during encephalomyocarditis virus infection

The double-stranded (ds) RNA-activated protein kinase from human cells is a 68,000 Mr protein (p68 kinase) induced by interferon. When autophosphorylated, p68 kinase catalyzes the phosphorylation of the protein synthesis eukaryotic initiation factor-2, thus mediating inhibition of protein synthesis. The level of p68 kinase is dramatically reduced in nonionic detergent NP-40 extracts, obtained from interferon-treated cells during infection with encephalomyocarditis virus (EMCV) (A. G. Hovanessian, 1. Galabru, E. Meurs, C. Buffet-Janvresse, J. Svab and N. Robert, Virology 159, 126–136, 1987). Here we show that such reduction of p68 kinase is in fact due to its reduced NP-40 solubility occurring during EMCV infection. However, p68 kinase can be recovered by extraction with an ionic detergent. Reduced NP-40 extractibility of p68 kinase is dependent on the multiplicity of virus infection and seems to be specific, since other cellular proteins as well as the 100-kDa 2′,5′-oligoadenylate synthetase also induced by interferon are not modified. Immunofluorescence studies using specific antibodies demonstrated that p68 kinase which is distributed evenly in the cytoplasm of HeLa cells becomes concentrated around the nuclei after EMCV infection. As a consequence of aggregating around the nuclei, p68 kinase might then resist extraction by NP-40. The aggregated kinase is found to be already activated probably due to binding to the replicative form and/or to replicative intermediates of EMCV RNA. Through this process, the functioning of p68 kinase might be guaranteed by a localized activation in the replication complexes of EMCV.

Binding properties of detergent-solubilized NCAM.

An assay has been designed for the identification of NCAM-binding proteins present in an NP-40 detergent extract of brain membranes. This method, which is capable of analyzing both heterophilic and homophilic interactions, uses species-specific antibodies against NCAM in combination with radioiodination, so that after unlabeled chicken and iodinated frog brain membrane proteins were allowed to interact, the chicken NCAM could be specifically isolated by immunoaffinity adsorption. The radiolabeled frog proteins coisolated with chicken NCAM were then characterized by one- and two-dimensional gel electrophoresis in combination with immunoblotting. The only detectable NCAM-binding proteins were identified as the 140- and 180-kD forms of NCAM. The presence and absence of polysialic acid on NCAM did not change the amount or nature of the frog proteins immunopurified under these conditions. As an alternative for detecting heterophilic ligands, a simplified immunoprecipitation method was employed using either iodine or sulfate radiolabels. Again under these conditions only NCAM was detected. These results are consistent with the hypothesis that the major binding protein for NCAM is NCAM itself, and suggest that differences in polysialic acid content do not directly alter the properties of NCAM's homophilic binding site.

Quantitative analysis of cell surface-associated SV40 large t antigen using a newly developed 3H-protein a binding assay

We have established a sensitive assay for the quantitative determination of large T antigen determinants on the surface of living simian virus 40 (SV40)-transformed cells (mKSA). Cells in suspension culture were incubated with monoclonal antibodies specific for large T antigen (KT3, directed against the carboxyterminus of large T antigen, and PAb 108, directed against an aminoterminal determinant on large T antigen). After incubation with secondary antibody (rabbit anti-mouse IgG), followed by incubation with 3H-protein A, the cells were sequentially extracted first with the nonionic detergent NP-40, followed by ultrasonication and extraction with the zwitterionic detergent Empigen BB. NP-40 solubilized large T antigen associated with NP-40-soluble constituents of the plasma membrane, whereas Empigen BB solubilized the plasma membrane lamina-associated subclass of large T antigen ( U. Klockmann and W. Deppert, 1983, EMBO J., 7, 1151–1157). The amount of cell surface-bound 3H-protein A in the NP-40 and Empigen BB extracts was determined by liquid scintillation counting. In agreement with earlier reports, cell surface large T antigen was mainly found in association with the plasma membrane lamina (PML). Since the specific activity of 3H-protein A was known, it was possible to calculate the number of surface-bound 3H-protein A molecules, and thus to estimate the average number of surface-exposed amino- and carboxyterminal determinants of large T antigen per cell. KT3 recognized about 450–900 carboxyterminal determinants, while PAb 108 bound to about 1200–2400 aminoterminal determinants on the surface of a single mKSA cell. The cellular protein p53 also was detected on the surface of mKSA cells and was found to be present in amounts comparable to cell surface large T antigen.

A monoclonal antibody, MA21, recognizes a surface component that is present on F9 teratocarcinoma cells and that appears vectorially on the trophectoderm of peri-implantation-stage mouse blastocysts

A monoclonal antibody (MAb) “MA21”, derived from lymphoid tissue of a multiparous mouse and selected for binding to mouse teratocarcinoma cell line F9, recognizes a surface antigen that appears on peri-implantation-stage mouse blastocysts. In indirect immunofluorescence assays, MAb MA21 does not bind to I-cell-through morula-stage embryos, nor to early, 3.5-day post-coitum (p.c.) blastocysts. When 3.5-day p.c. blastocysts are maintained 17 h in vitro and then assayed, MAb MA21 binds to a limited number of trophectoderm cells that are centered at the embryonic pole. As culture time lengthens, the number of antigen-expressing trophectoderm cells increases, forming a cap that spreads from the embryonic pole into the abembryonic region. Embryos maintained 48 h in vitro bind MAb MA21 over as much as 100% of the trophectoderm surface. MAb MA21 does not bind to the inner cell mass. When mouse pregnancy uteri are assayed by the immunoperoxidase method, MAb MA21 binds to extra-embryonic ectoderm and trophectoderm of 5-day p.c. implanted blastocysts, but does not bind to 6-day p.c. blastocysts. MAb MA21 recognizes a component with an estimated mol. wt of 44,000 from NP-40 detergent extracts of F9 cells and peri-implantation-stage mouse blastocysts. The component appears to be firmly associated with the plasma membrane; it is resistant to removal by high salt or moderate concentrations of non-ionic detergent.

Semliki forest virus particles containing only the E 1 envelope glycoprotein are infectious and can induce cell-cell fusion

Hydrophobic interaction chromatography (phenyl- and octyl-Sepharose) was performed with Semliki Forest virus to investigate the effect of low pH on its hydrophobicity. At neutral pH, the virus could be bound to the column and completely eluted by the detergent NP-40. Low pH treatment of virus prior to application to the column resulted in stronger binding as reflected by the increased amount of detergent necessary to totally elute the virus. If, however, the low pH treatment was done after binding of the virus to the column, only 15% of the input virus could be eluted by the detergent, indicating a drastic increase in hydrophobicity. Thus binding of the virus to a hydrophobic environment potentiates the effect of low pH on viral hydrophobicity. Trypsin digestion of column-bound virus after low pH treatment resulted in complete digestion of E 2 and E 3; however, E 1 was totally resistant. From this result, we conclude that E 1 alone is responsible for the hydrophobic interaction. We have made use of these observations to produce viral particles which were devoid of E 2 and E 3 by trypsin digestion in the presence of octyl glucoside. These E 1 viral particles were infectious and could induce membrane fusion. We conclude that only E 1 is necessary and sufficient to mediate membrane fusion. Acid pH induces a drastic increase in the hydrophobicity of E 1 which probably facilitates its interaction with the lipid bilayers during the fusion event in endosomes.

Rapid and quantitative preparation of cytoplasmic RNA from small numbers of cells

An extremely simple procedure for preparing cytoplasmic RNA from small numbers of cells is described. Cells are lysed with the detergent NP-40 and efficient extraction of protein from the postnuclear cytoplasmic lysate is ensured by denaturation with sodium dodecyl sulfate and urea. This procedure is suitable for preparing RNA from many cell types. All procedures have been scaled down to be performed in 1.5-ml microfuge tubes and thus RNA may be prepared from small numbers of cells. The procedure is extremely rapid and RNA is ready for Northern gel analysis in less than 30 min. Because so few steps are involved, RNA recovery is quantitative.

The signs of brain vulnerability in tardive dyskinesia : M. Marsalek, I. David, J. Pavlet, M. Petrovsky, L. Svab and P. Karen Institute of Psychiatry, Ustavni 91, 181 03 Prague, Czechoslovakia

The double-stranded (ds) RNA-activated protein kinase from human cells is a 68,000 Mr protein (p68 kinase) induced by interferon. When autophosphorylated, p68 kinase catalyzes the phosphorylation of the protein synthesis eukaryotic initiation factor-2, thus mediating inhibition of protein synthesis. The level of p68 kinase is dramatically reduced in nonionic detergent NP-40 extracts, obtained from interferon-treated cells during infection with encephalomyocarditis virus (EMCV) (A. G. Hovanessian, 1. Galabru, E. Meurs, C. Buffet-Janvresse, J. Svab and N. Robert, Virology 159, 126–136, 1987). Here we show that such reduction of p68 kinase is in fact due to its reduced NP-40 solubility occurring during EMCV infection. However, p68 kinase can be recovered by extraction with an ionic detergent. Reduced NP-40 extractibility of p68 kinase is dependent on the multiplicity of virus infection and seems to be specific, since other cellular proteins as well as the 100-kDa 2′,5′-oligoadenylate synthetase also induced by interferon are not modified. Immunofluorescence studies using specific antibodies demonstrated that p68 kinase which is distributed evenly in the cytoplasm of HeLa cells becomes concentrated around the nuclei after EMCV infection. As a consequence of aggregating around the nuclei, p68 kinase might then resist extraction by NP-40. The aggregated kinase is found to be already activated probably due to binding to the replicative form and/or to replicative intermediates of EMCV RNA. Through this process, the functioning of p68 kinase might be guaranteed by a localized activation in the replication complexes of EMCV.

Calcium-dependent cell-cell adhesion molecules (cadherins): subclass specificities and possible involvement of actin bundles.

Cadherins are a family of cell-cell adhesion molecules and are divided into subclasses with distinct adhesive specificities and tissue distribution. Here we examined the distribution of cadherins at contact sites between cells expressing the same or different cadherin subclasses. Each cadherin was concentrated at the boundary between cells expressing an identical cadherin subclass, irrespective of the cell types connected. However, such localization decreased or disappeared at the boundary between cells containing different cadherin subclasses. We also found that the localization of cadherins precisely coincided with that of actin bundles; both were detected at the apical region of cell sheets. This co-localization was retained even after cells were either treated with cytochalasin D or extracted with the detergent NP40. These results suggest that each cadherin subclass preferentially interacts with its own molecular type at intercellular boundaries, and that cadherin molecules may be associated with actin-based cytoskeletal elements.

Properties of a Hepatitis A Virus Candidate Vaccine Strain

This paper describes the biophysical and biochemical properties as well as electron microscopical studies of a candidate hepatitis A vaccine strain propagated in human fibroblast cells. Our results indicated that, in CsCl, the density of hepatitis A virus (HAV) from cell culture supernatant and of HAV extracted from infected cells was influenced by the quantity of lipid material associated with HAV. Antigenicity of untreated HAV, therefore, was detected primarily in low density CsCl fractions (1.11 g/ml, 1.21 g/ml). After lipid reduction with NP40 detergent or chloroform/Genetron, antigenicity and infectivity were primarily detected in high density CsCl fractions (1.31 g/ml). Electron microscopy demonstrated a strong association between membranous material and virus particles of low density in CsCl as well as virus-like particles in ultrathin sections of HAV-infected human fibroblast cells. The uncovered virus particles banded in the 1.31 g/ml dense CsCl fraction lacked lipid material. The s value was 79 for 1.19 g/ml to 1.22 g/ml dense HAV and 147 for 1.29 g/ml to 1.33 g/ml HAV. Autoradiography of the radioiodinated dense HAV revealed some proteins with high Mr (120K to 67K) and others with low Mr (37K to 15K).

Association of reovirus proteins with the structural matrix of infected cells

The interaction of reovirus with the cytoskeleton was investigated. The soluble components of infected cells were extracted with the nonionic detergent NP-40 in a physiological buffer, and a cytoskeletal extract was prepared from the detergent-insoluble fraction. We observed a selective association of viral-specified products with the cytoskeleton that was temporally controlled. Viral dsRNA appeared first on the framework but after several hours was found also in the soluble phase, encapsidated in mature virions. The initial viral translation products were associated exclusively with the soluble fraction, but concomitant with the appearance of dsRNA, viral proteins μ NS and σ 3 were detected on the cytoskeleton. Several hours later, all viral proteins were detected on the framework. Viral polypeptide μ NS exhibited unique spatial distribution patterns that correlated with viral assembly: Before dsRNA replication, it appeared as diffusely distributed protein; a few hours later, it was detected in punctate foci interconnected by tiny filaments; several hours later, it appeared as an extensive fiber network that traversed the foci. The other viral proteins were detected only within viral foci. μ NS remained bound to the matrix fraction after treatment with DNase, Mg 2+, and high salt, treatments that released other viral proteins. This distribution pattern was virus-directed because passage of virus at high multiplicity of infection induced mutations that prevented assembly of the μ NS-coated filament organization. A small fraction of the viral-specified products that included polypeptide μ NS, but not viral dsRNA, was coprecipitated from cytoskeletal extracts with proteins of mol wt ∼55K by monoclonal antibodies that recognized tubulin and vimentin. Disruption of this interaction by long exposure to colchicine did not prevent association of viral proteins or RNA with the matrix, indicating that viral products were not transported through these interactions. The results indicate that reovirus morphogenesis includes temporal and spatial controls not described previously.

Insulin-like activity of chromium-binding fractions from brewer's yeast

51CrCl 3 was added to the incubation medium of Saccharomyces cerevisiae for up to 48 hr. After repeated freezing and thawing, lysing in 9 M urea with 1% NP-40 detergent, and dialysis against water, the lower molecular weight (Mr < 3500) dialysate was retained on a SE53 cationic exchange column, eluted with 0.25 M NH 4OH and fractionated on a Bio-gel P-2 column. The insulinlike biological activity of the fractions was measured by the 14C-glucose oxidation in isolated rat adipocytes. The biological activity that was found in two of nine fractions did not correspond to their chromium content. Moreover, identical findings were obtained when chromium was added not to the live yeast but to the yeast extract, which showed that its binding was a chemical process not requiring cellular activity. No fraction demonstrated insulin-potentiating activity on rat adipocytes.

Interaction of mitogenic bacterial lipoprotein and a synthetic analogue with mouse lymphocytes. Isolation and characterization of binding proteins.

Lipoprotein from the outer membrane of Escherichia coli constitutes a potent mitogen and polyclonal activator for B lymphocytes of different species. The binding of lipoprotein to murine spleen cells was investigated using water-soluble 125I-labelled citraconylated lipoprotein from E. coli B/r. Our results indicate that the binding of this B-cell mitogen to splenocytes is a saturable, time- and dose-dependent, reversible process; about 9.7 X 10(8) lipoprotein molecules were bound to each cell. The mechanism of the binding of lipoprotein to lymphocytes was investigated by using the synthetic analogue of its N-terminal part, S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-N-palmitoyl-(R)-cysteinyl-( S)-seryl- (S)-seryl-(S)-asparaginyl-(S)-alanine (tripalmitoyl pentapeptide). This compound had been shown by us previously to be the molecular part of lipoprotein responsible for mitogenicity and exhibited, in all experiments performed, a stimulatory activity towards B lymphocytes comparable, or even superior, to native lipoprotein. Binding proteins for the synthetic N-terminus were enriched by affinity chromatography, using an affinity column prepared by coupling the mitogenic compound to CPG-aminopropyl controlled-pore glass beads by the carbodiimide method. [3H]Leucine-labelled murine spleen cells were solubilized by the nonionic detergent NP40 and applied to the affinity adsorbent. Proteins bound to the column were selectively eluted by a solution of tripalmitoyl pentapeptide, and the fractions were analyzed by sodium dodecyl sulphate/polyacrylamide gel electrophoresis and autoradiography. Our results indicate the presence of a major binding protein of Mr 35000 on mouse primary lymphocytes for the biologically active N-terminal structure of lipoprotein, which might play a role as membrane receptor in mitogenic B lymphocyte activation.

Identification of a 150-kDa membrane component which is modulated by parathyroid hormone.

Monoclonal antibodies have been produced against primary bone cells obtained from the collagenase digestion of mouse cranial bone. Antibodies were selected on the basis of their immunoglobulin class and those which were identified as IgG were further screened for their ability to inhibit cAMP accumulation in response to sub-maximal doses of the 1-34 amino-terminal peptide of bovine parathyroid hormone, bPTH(1-34). Nine hybridoma clones were subsequently characterized as inhibitory with respect to parathyroid hormone (PTH) responses in intact mouse cranial bone and which also identified a variety of membrane components from detergent extracts of surface-labeled primary bone cells. Five of these antibodies immunoprecipitated a membrane component with Mr of 80 000 that appeared to be a major component of the extract susceptible to surface-labeling with 125I. All nine monoclonal antibodies were shown to bind to a suspended-cell preparation of primary bone cells with 2-3 orders of magnitude greater binding than that of control antibodies. Using this assay, one clone, designated 3G12 IgG, was observed to exhibit desensitization effects at the binding level with a time course and dose dependency for PTH pre-incubation that was similar to the establishment of the refractory state in other systems. In addition, the desensitization effect occurred at 37 degrees C but not at 4 degrees C. This antibody was shown to bind saturably to both intact mouse cranial bone and primary bone cells with an apparent affinity constant (Ka) in the range of 10(9) M. Inhibition of bone cAMP accumulation in response to 2.5 nM bPTH(1-34) was directly correlated to the binding of 3G12 IgG to intact mouse calvariae. A maximum inhibition of approximately 85% was observed. 3G12 IgG immunoprecipitated a single membrane component, Mr 150 000, from NP-40 detergent extracts of 125I-labeled primary mouse bone cells. The molecular mass of this component was also 150 000 daltons when run on polyacrylamide gel slabs under non-reducing conditions. Control and PTH-pre-treated bone cells were surface-labeled, detergent-solubilized and immunoprecipitated with 3G12 IgG in order to investigate further the desensitization effect at the molecular level. Incubation of bone cells with 1 microgram/ml bPTH(1-34) for 45 min at 37 degrees C caused an increased susceptibility to surface-labeling with 125I that was approximately three-fold higher in specific activity than that of control cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Disinfection and inactivation of the human T lymphotropic virus type III/Lymphadenopathy-associated virus.

This study was aimed at investigating the inactivation by reagents and conditions commonly used in research laboratories of human T-lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV). The following proposed inactivators were tested: isopropyl rubbing alcohol ethyl alcohol absolute alcohol household bleach Tween-20 paraformaldehyde Lysol and H202. Separate tubes of virus and inactivator were 1st serially diluted and then inoculated together into cell cultures. A sensitive and quantitative bioassay for infectious virus was used to evaluate virus inactivation. Both the observed reduction in titer of infectious virus after exposure to disinfectants (interpreted by comparison with appropriate controls) and empirical estimates of efficacy derived by extrapolation from dose-response plots were used as indicators of virus inactivation. The results indicate that alcohols hypochlorite the detergent NP-40 (but not Tween-20) H202 phenolics and paraformaldehyde are all effective inactivators of HTLV-III/LAV at concentrations well below those usually formulated for use as a disinfectant or in laboratories. These findings can be applied to dried virus as well provided that disinfection procedures result in penetration of disinfectant into dried material or cause dissolution or suspension of the virus into disinfectant. These data should be of interest to laboratory personnel and others who are concerned with potential exposure to the acquired immunodeficiency syndrome (AIDS).