Photocatalytic Anti-Markovnikov Radical Hydro- and Aminooxygenation of Unactivated Alkenes Tuned by Ketoxime Carbonates

A tunable photocatalytic method is reported for anti-Markovnikov hydro- and aminooxygenation of unactivated alkenes using readily accessible ketoxime carbonates as the diverse functionalization reagents. Mechanistic studies reveal that this reaction is initiated through an energy-transfer-promoted N-O bond homolysis of ketoxime carbonates leading to alkoxylcarbonyloxyl and iminyl radicals under visible-light photocatalysis, followed by the addition of alkoxylcarbonyloxyl radical to alkenes. By taking advantage of the different stability of the iminyl radicals, the generated carbon radical either abstracts a hydrogen atom from the media to form the anti-Markovnikov hydrooxygenation product, or it is trapped by the persistent iminyl radical to furnish the aminooxygenation product. Notably, this is the first example of direct hydrooxygenation of unactivated olefins with anti-Markovnikov regioselectivity involving an oxygen-centered radical.

Electrochemically Tuned Oxidative [4+2] Annulation and Dioxygenation of Olefins with Hydroxamic Acids

This work represents the first [4+2] annulation of hydroxamic acids with olefins for the synthesis of benzo[c][1,2]oxazines scaffold via anode-selective electrochemical oxidation. This protocol features mild conditions, is oxidant free, shows high regioselectivity and stereoselectivity, broad substrate scope of both alkenes and hydroxamic acids, and is compatible with terpenes, peptides, and steroids. Significantly, the dioxygenation of olefins employing hydroxamic acid is also successfully achieved by switching the anode material under the same reaction conditions. The study not only reveals a new reactivity of hydroxamic acids and its first application in electrosynthesis but also provides a successful example of anode material-tuned product selectivity.

Fork gratings based on ferroelectric liquid crystals

In this article, we disclose a fork grating (FG) based on the photo-aligned ferroelectric liquid crystal (FLC). The Digital Micro-mirror Device based system is used as a dynamic photomask to generated different holograms. Because of controlled anchoring energy, the photo alignment process offers optimal conditions for the multi-domain FLC alignment. Two different electro-optical modes namely DIFF/TRANS and DIFF/OFF switchable modes have been proposed where the diffraction can be switched either to no diffraction or to a completely black state, respectively. The FLC FG shows high diffraction efficiency and fast response time of 50µs that is relatively faster than existing technologies. Thus, the FLC FG may pave a good foundation toward optical vertices generation and manipulation that could find applications in a variety of devices.

Protein phosphorylation affects binding of the Escherichia coli transcription activator UhpA to the uhpT promoter

Expression of the Escherichia coli sugar phosphate transporter UhpT is induced by extracellular glucose 6-phosphate through a transmembrane signaling process dependent on the sensor kinase UhpB and the UhpT homolog, UhpC. These proteins are thought to regulate the phosphorylation of the transcription activator, UhpA. To examine the effect of protein phosphorylation on the binding of UhpA to target sequences in the uhpT promoter region, the UhpA protein was overexpressed and purified. Purified UhpA was phosphorylated by acetyl phosphate in a reaction that was dependent on Mg2+ and on the presence of aspartate 54, the site of phosphorylation in homologous response regulators. Gel electrophoretic mobility shift and DNase I and hydroxyl radical protection assays showed that UhpA bound specifically to the region of the uhpT promoter extending from -80 to -50 bp, relative to the transcription start site. At higher concentrations of UhpA, binding was extended to the -32 region. Binding to the -64 element exhibited positive cooperativity and was stimulated severalfold by phosphorylation of UhpA, whereas extension to the downstream region was more strongly affected by phosphorylation. The consensus sequences for the high affinity UhpA-binding sites in the -64 element and for the downstream, low affinity sites are proposed. The pattern of in vitro binding by UhpA agreed with the in vivo observations that phosphorylation-independent assembly of the transcription initiation complex can occur at elevated concentrations of UhpA.

Sequences of the Escherichia coli BtuB protein essential for its insertion and function in the outer membrane

The Escherichia coli btuB gene encodes the outer membrane transporter for vitamin B12, the E colicins, colicin A, and bacteriophage BF23. Several series of mutant forms of BtuB resulting from the insertion of dipeptide sequences and from overlapping in-frame deletions and duplications were constructed. Strains expressing the variant genes in single and multiple copy numbers were analyzed for BtuB function, for the level of BtuB polypeptide in the outer membrane, and for changes in the outer membrane permeability barrier. Most dipeptide insertions had normal transport function and assembly in the membrane. Only 2 of the 27 deletions spanning residues 5 and 514 possessed transport function, and most of the remainder were not stably inserted in the membrane. Most duplications (19 of 21) retained transport function and were inserted in the outer membrane, although some were subject to proteolysis. Even long duplications containing as many as 340 repeated amino-terminal residues retained function, suggesting considerable plasticity in the sequence requirements for membrane insertion of BtuB. Expression of many deletion and duplication proteins conferred increased susceptibility to structurally unrelated inhibitors that are normally excluded by the outer membrane. These results could be consistent with the mutational disruption of extracellular loops or transmembrane segments of BtuB that constitute a gated channel, but the finding that alterations throughout the length of BtuB affect membrane permeability properties suggests that the altered proteins might perturb the outer membrane structure itself.

Substitution of class II alpha chain polymorphic residues defines location of A alpha k serologic epitopes and alters association between alpha beta and Ii polypeptides

Structure-function studies of the MHC class II alpha chain have been performed by constructing a panel of A alpha k cDNA genes with one or more d allele substitutions at each polymorphic residue of the alpha 1 domain. The altered genes (A alpha k*) were transfected into a B lymphoma cell line (BKO), which is deficient in A alpha mRNA but retains constitutive wild-type A beta k mRNA expression. Cytofluorometric analysis of cell surface A alpha k* Ak beta molecules was used to map the polymorphic alpha chain residues comprising four serologic epitopes. A alpha k-reactive mAbs 1E9, 2A2, and 3F12 recognize an epitope that includes the polymorphic residue 44 of the A alpha k polypeptide, and the A alpha k-reactive antibody, K24-199, recognizes a conformationally determined epitope influenced by residues from all three polymorphic regions. In addition, we confirmed previous studies demonstrating that la.19 and la.2 mAbs bind to epitopes adjacent to residue 75 in A alpha k. A cell surface negative expression variant also was identified in the panel of mutant cell lines and biochemically characterized. Substitution of six d allele polymorphic residues at positions 11, 14, 28, 69, 70, and 75 in the A alpha k polypeptide (T.EG A alpha k* A beta k*) results in an A alpha k* polypeptide that associates with the A alpha k polypeptide but does not associate with the li polypeptide. This defect in li-A alpha k A beta k interaction is associated with a conformational change in the alpha 1 beta 1 domain that was identified by altered reactivity of the T.EG complex with conformationally dependent anti-alpha and anti-beta mAbs.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of MHC class II A alpha k transgene. Pairing with endogenous beta-chain is dependent upon affinity and competition

Studies on cell lines transfected with MHC class II genes have revealed important limitations on the assembly of haplotype-mismatched A alpha/A beta complexes. We have investigated pairing restriction in vivo by analyzing transgenic mice that carry an A alpha k gene on several H-2 haplotypes. Previously, we reported the A alpha k transgenic expression on the cell surface of H-2b and H-2u strains. Further transcomplementation studies performed with high A alpha k-expressing transgenic lines revealed that A alpha k chain can pair with A beta b,s,f,d,v, or u chains but not with A beta q. Homozygosity for the A alpha k transgene increased the expression of mixed heterodimers. The inefficient assembly of haplotype-mismatched class II polypeptides results from their inability to compete with the matched pairs. The higher affinity between the matched pairs can be overcome by increased synthesis of the mismatched pair. Thus, there is no "strict" sequence-based restrictions on pairing.

Triterpenoid glycosides from Decaisnea fargesii

Five new triterpenoid glycosides designated decaisosides A-E together with five known ones were isolated from the stems of Decaisnea fargesii. Their structures were established by means of chemical and spectroscopic evidence.

Conserved structural and regulatory regions in the Salmonella typhimurium btuB gene for the outer membrane vitamin B12 transport protein

The Salmonella typhimurium btuB gene encodes an outer membrane protein that is necessary for the transport of vitamin B12 and the uptake of the E colicins and bacteriophage BF23. The sequence of this gene showed 87% identity of the deduced polypeptide to its Escherichia coli homolog, and its product was found to function in transport as effectively in cells of E. coli as did the native protein. The extensive sequence conservation within the first 300 transcribed nucleotides, which include the leader and early part of the coding sequence, supports the proposed role of this region in the regulation of btuB gene expression.

Structure and function of the uhp genes for the sugar phosphate transport system in Escherichia coli and Salmonella typhimurium

Expression of the Escherichia coli sugar phosphate transport system, encoded by the uhpT gene, is regulated by external glucose 6-phosphate through the action of three linked regulatory genes, uhpABC. The nucleotide sequence of the uhp region cloned from Salmonella typhimurium was determined. The deduced Uhp polypeptide sequences from the two organisms are highly related. Comparison with the corrected sequence from E. coli revealed that the four uhp genes are closely spaced, with minimal intergenic distances, and that uhpC is nearly identical in length to uhpT, both of which have substantial sequence relatedness along their entire lengths. To facilitate analysis of uhp gene function, we isolated insertions of a kanamycin resistance (Km) cassette throughout the uhp region. In-frame deletions that removed almost the entire coding region of individual or multiple uhp genes were generated by use of restriction sites at the ends of the Km cassette. The phenotypes of the Km insertions and the in-frame deletions confirmed that all three regulatory genes are required for Uhp function. Whereas the deletion of uhpA completely abolished the expression of a uhpT-lacZ reporter gene, the deletion of uhpB or uhpC resulted in a partially elevated basal level of expression that was not further inducible. These results indicated that UhpB and perhaps UhpC play both positive and negative roles in the control of uhpT transcription. Translational fusions of the uhpBCT genes to topological reporter gene phoA were generated by making use of restriction sites provided by the Km cassette or with transposon TnphoA. The alkaline phosphatase activities of the resultant hybrid proteins were consistent with models predicting that UhpC and UhpT have identical transmembrane topologies, with 10 to 12 transmembrane segments, and that UhpB has 4 to 8 amino-terminal transmembrane segments that anchor the polar carboxyl-terminal half of the protein to the cytoplasmic side of the inner membrane.

Host dependence of naturally occurring temperature-sensitive influenza A viruses and location of their genetic lesions

Naturally occurring temperature-sensitive (ts) strains have been found in large number in human influenza A viruses of all subtypes (J. Virol. 41 (1982) 353). Further studies have demonstrated that the ts phenotype of these viruses is host-dependent in that they are highly ts in chick embryos and chick embryonic cells, but are ts+ in MDCK cells. Previous studies have located by complementation tests the ts lesion of two H3N2 viruses (HK/8/68 and Ningxia/01/72, also known as Xia-ts) on the NP gene and that of two H1N1 viruses (Tianjin/78/77 and Beijing/1/79) on the M protein gene. By recombination and polyacrylamide electrophoresis migration of the RNA segments of its ts+ recombinant with PR8, the ts lesion of a later H3N2 virus A/Qi/39/79 has now been located on the M protein gene. The possibility for Qi/39/79 of acquiring the M gene lesion by reassortment with concurrently circulating Tianjin/78/77-like (H1N1) virus which also has ts lesion on the M gene was investigated. In contrast to Tianjin/78/77 (H1N1), however, Qi/39/79 complemented well with ts 51, a WSN ts strain with a single M gene lesion. Qi/39/79 and Tianjin/78/77 also complemented each other. Thus, there are two intra-segmental complementation groups of the M gene: Qi/39/79 belongs to one complementation group, while WSN ts 51 and Tianjin/78/77 belong to another. At present, there is no evidence of reassortment involving the genes concerned in the ts lesions of H3N2 and H1N1 viruses under natural conditions.

Local structure of a peptide contact site on Ak alpha

We have sought to determine how much amino acid diversity is tolerable at position 69 of the Ak alpha chain, a position previously implicated as a peptide contact site. Slot-machine mutagenesis was used to create a set of 11 mutant Ak alpha cDNAs, each specifying a different amino acid at position 69. These cDNAs were individually expressed in L cells together with a wild-type Ak beta cDNA to produce a panel of mutant antigen-presenting cell lines. The ability of each member of this panel to present a hen egg lysozyme and a bovine ribonuclease peptide to various T hybridomas was assessed. We found that a surprising degree of amino acid diversity is tolerable at Ak alpha position 69: even charged (Glu, Arg) or bulky (Trp, Tyr) residues can be accommodated without abrogating cell-surface expression of Ak, peptide binding to it, or T cell recognition of it. We discuss the implications of these findings for models of T cell recognition of the class II molecule/antigen duplex.

Functional effects of N-linked oligosaccharides located on the external domain of murine class II molecules

To evaluate the potential functional role of the alpha- and beta-chain N-linked oligosaccharides we used site-directed mutagenesis to construct class II Ak alpha and Ak beta genes that encode polypeptides with altered N-linked oligosaccharide acceptor sites in the N-terminal domain of both polypeptides. The alpha 1 domain acceptor site at positions 82 to 84 was eliminated by substituting Gln for Asn at position 82. The beta 1 domain acceptor site at positions 19 to 21 was deleted by substituting Gln for Asn at position 19 or Ala for Thr at position 21. The mutant genes (Ak alpha* or Ak beta*) were transfected either individually (mutants T.19, T.21, and T.82) or together (mutant T.82-21) into class II cell surface negative B lymphoma cell lines. Quantitative immunofluorescence with a panel of Ak beta- or Ak alpha- reactive mAb demonstrated that although the oligosaccharide-deleted Ak alpha Ak beta molecules were serologically wild type, the Ad alpha serologic epitope defined by mAb K24-199 was eliminated in both the T.19 and T.21 Ak beta* Ad alpha molecules. Cloned cell lines expressing the T.19 or T.21 Ak beta* Ak alpha molecules exhibited limited functional Ag presentation defects. Cells expressing the T.82 Ak alpha* Ak beta molecules exhibited defects in Ag presentation function to nine of the ten T hybridomas tested. Surprisingly, cells expressing the mutant T.82-21 class II molecule stimulated a response that was equal to the wild-type response from three of the nine T hybrids and a response that was significantly greater than that of wild-type cells from five of nine T hybridomas. These functional and serological analyses also indicate that some of the observed Ag presentation defects may be due to altered secondary structure caused by either deletion of the oligosaccharide or the amino acid substitution used to delete the N-linked oligosaccharide acceptor site.

Functional effects of N-linked oligosaccharides located on the external domain of murine class II molecules

To evaluate the potential functional role of the alpha- and beta-chain N-linked oligosaccharides we used site-directed mutagenesis to construct class II Ak alpha and Ak beta genes that encode polypeptides with altered N-linked oligosaccharide acceptor sites in the N-terminal domain of both polypeptides. The alpha 1 domain acceptor site at positions 82 to 84 was eliminated by substituting Gln for Asn at position 82. The beta 1 domain acceptor site at positions 19 to 21 was deleted by substituting Gln for Asn at position 19 or Ala for Thr at position 21. The mutant genes (Ak alpha* or Ak beta*) were transfected either individually (mutants T.19, T.21, and T.82) or together (mutant T.82-21) into class II cell surface negative B lymphoma cell lines. Quantitative immunofluorescence with a panel of Ak beta- or Ak alpha- reactive mAb demonstrated that although the oligosaccharide-deleted Ak alpha Ak beta molecules were serologically wild type, the Ad alpha serologic epitope defined by mAb K24-199 was eliminated in both the T.19 and T.21 Ak beta* Ad alpha molecules. Cloned cell lines expressing the T.19 or T.21 Ak beta* Ak alpha molecules exhibited limited functional Ag presentation defects. Cells expressing the T.82 Ak alpha* Ak beta molecules exhibited defects in Ag presentation function to nine of the ten T hybridomas tested. Surprisingly, cells expressing the mutant T.82-21 class II molecule stimulated a response that was equal to the wild-type response from three of the nine T hybrids and a response that was significantly greater than that of wild-type cells from five of nine T hybridomas. These functional and serological analyses also indicate that some of the observed Ag presentation defects may be due to altered secondary structure caused by either deletion of the oligosaccharide or the amino acid substitution used to delete the N-linked oligosaccharide acceptor site.

A single amino acid substitution in the Ak molecule fortuitously provokes an alloresponse

We discovered by chance that the R28 T cell hybridoma has dual specificity. It responds to a peptide derived from ribonuclease presented by cells displaying Ak molecules and it reacts, in the absence of added antigen, to cells expressing Ak complexes with a single amino acid substitution at position 69 of the alpha chain. Modelling and functional studies suggest that residue 69 is a peptide contact residue, prompting the hypothesis that R28's alloreactivity is a cross-reactive response to an unknown peptide bound in the 'groove' of the mutant Ak complex. In this report, we employ a competition assay to confirm that this alloresponse involves a groove-binding peptide, demonstrate that this peptide derives from or depends on fetal calf serum and exploit a panel of antigen-presenting cell lines--each displaying an Ak complex with a different position 69 substitution--to establish that the alloresponse is not just a heteroclitic response to ribonuclease, itself. We speculate that much of the alloreactivity against murine class II molecules that is revealed in vitro may prove to be directed at bovine serum-derived peptides, suggesting that in this context, alloreactivity is a misnomer.

Expression and function of mutant Ia antigen in transgenic mice

Cell surface expression of Ia antigens requires the assembly of alpha and beta heterodimers. We have produced a double transgenic mouse with a wild form Ak alpha gene and a mutant Ak beta (Ak beta MB) gene with d-allele substitution at positions 63 and 65-67. Initial studies indicated that the Ak alpha and Ak beta MB transgenes are not expressed on the surface of lymphoid cells of the transgenic mice. However, when spleen cells were stimulated with LPS prior to FACS analyses, Ak/Ak MB assembly and subsequent surface expression was induced. The tail skins from transgenic founder mice were rejected by the parental mice indicating a role for the mutant antigen on the allograft. In addition, the Ak transgenic mice on H-2q/q background can partially delete V beta 6+ T cells, suggesting the presence of the transgene product in the thymus.

Immunosuppression of collagen-induced arthritis in mice with an anti-IL-2 receptor antibody

The use of an anti-IL-2R antibody, 7D4, was investigated in vivo in the suppression of collagen-induced arthritis in mice. 7D4 was shown to reduce the incidence of arthritis in a group of mice immunized with type II collagen as compared with a group similarly immunized with collagen and treated with a control isotype matched anti-Forsmann antibody. 7D4 was also shown to reduce the severity of arthritis in the treated mice as compared to the mice in the group treated with the control antibody. Anti-IL-2R antibodies may be useful in the treatment of autoimmune diseases by selectively suppressing activated T cells.

Immunosuppression of collagen-induced arthritis in mice with an anti-IL-2 receptor antibody

The use of an anti-IL-2R antibody, 7D4, was investigated in vivo in the suppression of collagen-induced arthritis in mice. 7D4 was shown to reduce the incidence of arthritis in a group of mice immunized with type II collagen as compared with a group similarly immunized with collagen and treated with a control isotype matched anti-Forsmann antibody. 7D4 was also shown to reduce the severity of arthritis in the treated mice as compared to the mice in the group treated with the control antibody. Anti-IL-2R antibodies may be useful in the treatment of autoimmune diseases by selectively suppressing activated T cells.

Suppression of the murine anti-trimellityl (TM) IgE response: induction of B cell tolerance by conjugates of TM and polyvinyl alcohol

It was previously shown that administration of conjugates of trimellitic anhydride with polyvinyl alcohol (TM-PVA) could suppress the IgE anti-TM immune response of mice sensitized with a TM-ovalbumin conjugate. In the present study, the existence of TM-specific B cell tolerance was shown by cell transfer experiments in which splenic B cells from mice treated with TM-PVA failed to interact with either the helper T (Th) cells of carrier primed recipients or with Th cells derived from carrier-primed donors. In contrast to previous findings from this laboratory indicating that tolerogenic conjugates of PVA and the 2,4-dinitrophenyl group led to both B cell tolerance and activation of suppressor T (Ts) cells, no evidence was obtained for the induction of Ts cells by TM-PVA. Thus, the induction of demonstrable Ts cells by hapten-PVA conjugates may depend on some property conferred by the haptenic group.

Suppression of the anti-trimellityl (TM) IgE response in mice by conjugates of TM with polyvinyl alcohol

The i.p. injection of 1 microgram of TM3-OA or TM9-OA with 1 mg of A1(OH)3 into B6D2F1 mice elicited the production of antibodies of the IgE and other classes to the trimellityl (TM) group and ovalbumin (OA). The induction of anti-TM antibodies belonging to the IgE and other immunoglobulin classes was specifically suppressed by the administration of tolerogenic conjugates prepared by coupling trimellitic anhydride (TMA) to the hydrophilic non-immunogenic polymer, polyvinyl alcohol (PVA), prior to immunization with TM-OA conjugates. More importantly, established anti-TM responses were also suppressed by these TM-PVA conjugates. By contrast, however, treatment with TM-PVA conjugates did not affect either the primary or the established anti-OA antibody response. The tolerogenic effects of the PVA conjugates were dose-dependent and appeared also to be dependent on the epitope density. Treatment with these conjugates also prevented immunized mice from showing any symptoms of systemic anaphylaxis on challenge with polyvalent TM-protein conjugates. These findings indicate that these conjugates may have the potential of useful therapeutic agents for the treatment of TMA-induced pulmonary hypersensitivity diseases.