Applied Biosystems

About: Applied Biosystems is a based out in . It is known for research contribution in the topics: Mass spectrometry & Nucleic acid. The organization has 1521 authors who have published 1579 publications receiving 285423 citations.

Impact of HIV on cell survival and antiviral activity of plasmacytoid dendritic cells.

Abstract: Plasmacytoid dendritic cells (pDCs) are important mediators of innate immunity that act mainly through secretion of interferon (IFN)-α. Previous studies have found that these cells can suppress HIV in vitro; additionally, pDCs have been shown to be severely reduced in the peripheral blood of HIV-infected individuals. In the present study, we sought to determine the ability of pDCs to directly suppress viral replication ex vivo and to delineate the potential mechanisms whereby pDCs are depleted in HIV-infected individuals. We demonstrate that activated pDCs strongly suppress HIV replication in autologous CD4+ T cells via a mechanism involving IFN-α as well as other antiviral factors. Of note, unstimulated pDCs from infected individuals who maintain low levels of plasma viremia without antiretroviral therapy were able to suppress HIV ex vivo via a mechanism requiring cell-to-cell contact. Our data also demonstrate that death of pDCs by both apoptosis and necrosis is induced by fusion of HIV with pDCs. Taken together, our data suggest that pDCs play an important role in the control of HIV replication and that high levels of viral replication in vivo are associated with pDC cell death via apoptosis and necrosis. Elucidation of the mechanism by which pDCs suppress HIV replication in vivo may have clinically relevant implications for future therapeutic strategies.

A Cleavage Method which Minimizes Side Reactions Following Fmoc Solid Phase Peptide Synthesis.

Abstract: The success of solid phase peptide synthesis utilizing 9-fluorenylmethoxycarbonyl (Fmoc) amino acids is often limited by deleterious side reactions which occur during TFA peptide-resin cleavage and side-chain deprotection. The majority of these side reactions modify susceptible residues, such as Trp, Tyr, Met, and Cys, with TFA-liberated side-chain protecting groups and linkers. The purpose of this study was to assess the relative effectiveness of various scavengers in suppressing these side reactions. We found that the cleavage mixture 82.5% TFA : 5% phenol : 5% H2O : 5% thioanisole : 2.5% EDT (Reagent K) was maximally efficient in inhibiting a great variety of side reactions. Synthesis and cleavage of 10 peptides, each containing 20-50 residues, demonstrated the complementarity of Fmoc chemistry with Reagent K for efficient synthesis of complex peptides.

Molecular and immunohistochemical characterization of the onset and resolution of human renal allograft ischemia-reperfusion injury.

Abstract: BACKGROUND Following allotransplantation, renal ischemia-reperfusion (I/R) injury initiates a series of events that provokes counter-adaptive immunity. Though T cells clearly mediate allospecific immunity, the manner in which reperfusion events augment their activation has not been established. In addition, comprehensive analysis of I/R injury in humans has been limited. METHODS To evaluate the earliest events occurring following allograft reperfusion and gain insight into those factors linking reperfusion to alloimmunity, we examined human renal allografts 30 to 60 minutes postreperfusion (n=10) and compared them with allografts with normal function that had resolved their I/R injury insult (>1 month posttransplant, n=6) and to normal kidneys (living donor kidneys before procurement, n=8). Biopsies were processed both for immunohistochemical analysis as well as for transcript analysis by real-time quantitative polymerase chain reaction (RT-PCR). RESULTS Reperfusion injury was characterized by increased levels of gene transcripts known to be involved in cellular adhesion, chemotaxis, apoptosis, and monocyte recruitment and activation. T-cell-associated transcripts were generally absent. However, recovered allografts exhibited increased levels of T-cell and costimulation-related gene transcripts despite normal allograft function. Consistent with these findings, the immediate postreperfusion state was characterized histologically by tubular injury and monocyte infiltration, while the stable posttransplant state was notable for T-cell infiltration. CONCLUSIONS These data suggest that monocytes and transcripts related to their recruitment dominate the immediate postreperfusion state. This gives way to a T-cell dominant milieu even in grafts selected for their stable function and absence of rejection. These data have implications for understanding the fundamental link between I/R injury and alloimmunity.

Automated polypeptide synthesis apparatus

Abstract: An apparatus is provided for automatically constructing a polypeptide of high purity, up to 50 amino acids in length, using only single couplings. The apparatus includes an ac- ivation system for receiving protected amino acids, one kind at a time, having a common vessel (an activator vessel) in which to activate each of the amino acids. Also included is ; reaction vessel for containing a resin used in solid-phase I eptide synthesis for attaching a peptide chain thereto. A transfer system is also provided, which operates under con- rol of a computer, to transfer the activated species from the ctivation system to the reaction vessel and to transfer amino acids, reagents, gases, and solvents from one part of the apparatus to another. The activator system also includes a temperature controlled concentrator vessel in which an activator solvent is replaced by a coupling solvent to enhance the coupling of the activated species to the peptide chain in the reaction vessel. Also included in the synthesizer system is a vortexer for affecting total washing of materials in the .reaction vessel and the reaction vessel itself, an automated peptide resin sampling system, and an autodelivery system for providing individual containers of amino acid to the synthesizer in the order desired in the peptide seauence. A liquid sensor system is also included to monitor transitions between gases and liquids in specific tubes in the synthesizer in order to provide input signals to the computer system for control purposes. The computer system software which controls the operation of the synthesizer is organized according to a series of menus which allows the user of the system to select individual cycles of operation for each vessel in the synthesizer. In addition, an algorithm has been developed which provides for optimum efficiency in the production of a peptide for any given selection of cycles.