Quick attach and release fluid coupling assembly is self-aligning, self-sealing

Fluid coupling assembly that is self-aligning, self-sealing and contains a bellow ball and socket coupling for quick attach and release is highly reliable and can handle cryogenic fluids where icing is encountered. The fluid coupling assembly is used in many fluid systems but is particularly applicable to cryogenic systems

Investigation of catalysis by bacterial RNase P via LNA and other modifications at the scissile phosphodiester

We analyzed cleavage of precursor tRNAs with an LNA, 2′-OCH3, 2′-H or 2′-F modification at the canonical (c0) site by bacterial RNase P. We infer that the major function of the 2′-substituent at nt −1 during substrate ground state binding is to accept an H-bond. Cleavage of the LNA substrate at the c0 site by Escherichia coli RNase P RNA demonstrated that the transition state for cleavage can in principle be achieved with a locked C3′ -endo ribose and without the H-bond donor function of the 2′-substituent. LNA and 2′-OCH3 suppressed processing at the major aberrant m−1 site; instead, the m+1 (nt +1/+2) site was utilized. For the LNA variant, parallel pathways leading to cleavage at the c0 and m+1 sites had different pH profiles, with a higher Mg2+ requirement for c0 versus m+1 cleavage. The strong catalytic defect for LNA and 2′-OCH3 supports a model where the extra methylene (LNA) or methyl group (2′-OCH3) causes a steric interference with a nearby bound catalytic Mg2+ during its recoordination on the way to the transition state for cleavage. The presence of the protein cofactor suppressed the ground state binding defects, but not the catalytic defects

Structural and functional insight into the mechanism of an alkaline exonuclease from Laribacter hongkongensis

Alkaline exonuclease and single-strand DNA (ssDNA) annealing proteins (SSAPs) are key components of DNA recombination and repair systems within many prokaryotes, bacteriophages and virus-like genetic elements. The recently sequenced β-proteobacterium Laribacter hongkongensis (strain HLHK9) encodes putative homologs of alkaline exonuclease (LHK-Exo) and SSAP (LHK-Bet) proteins on its 3.17 Mb genome. Here, we report the biophysical, biochemical and structural characterization of recombinant LHK-Exo protein. LHK-Exo digests linear double-stranded DNA molecules from their 5′-termini in a highly processive manner. Exonuclease activities are optimum at pH 8.2 and essentially require Mg2+ or Mn2+ ions. 5′-phosphorylated DNA substrates are preferred over dephosphorylated ones. The crystal structure of LHK-Exo was resolved to 1.9 Å, revealing a ‘doughnut-shaped’ toroidal trimeric arrangement with a central tapered channel, analogous to that of λ-exonuclease (Exo) from bacteriophage-λ. Active sites containing two bound Mg2+ ions on each of the three monomers were located in clefts exposed to this central channel. Crystal structures of LHK-Exo in complex with dAMP and ssDNA were determined to elucidate the structural basis for substrate recognition and binding. Through structure-guided mutational analysis, we discuss the roles played by various active site residues. A conserved two metal ion catalytic mechanism is proposed for this class of alkaline exonucleases

Dry Gas Seal System Design Standards For Centrifugal Compressor Applications.

Tutorialpg. 145-152Dry gas seals have been applied in process gas centrifugal compressors for more than 20 years. Over 80 percent of centrifugal gas compressors manufactured today are equipped with dry gas seals. Despite the 20-year trend of increasing dry gas seal applications, and industry accepted standard for gas seal support system design does not exist. The American Petroleum Institute (API) has only recently addressed gas seal system design in its Standard 614 (1999). This paper proposes a set of gas seal system design standards for process gas centrifugal compressors on the basis of safety, reliability, and economics. This paper presents the philosophy of one centrifugal compressor and dry gas seal original equipment manufacturer (OEM) in regard to gas seal system design standards. These standards are based on over 20 years of experience in the area of gas seal system design, drawing form actual field experience of thousands of compressors. The reader shall recognize, however, that numerous gas seal system design philosophies can be applied to achieve the same system objectives

Mechanical Upgrades To Improve Centrifugal Compressor Operation And Reliability.

Tutorialpg. 157-156In today’s business environment, centrifugal compressor reliability is more critical than ever. Unscheduled equipment downtime has a negative impact on plant operations, oftentimes resulting in a temporary halt of production. In most centrifugal compressor applications, loss of production results in a substantial loss of revenue, sometimes measured in the hundreds of thousands or even millions of dollars per day. This lost revenue has a direct impact on the profitability of the plant. There are tens of thousands of centrifugal compressors currently operating with outdated technology, resulting in increased maintenance costs and reduced reliability. However, product upgrades can improve compressor operation and increase reliability and availability by incorporating the latest technology into existing rotating equipment. The initial investment for these mechanical upgrades is very low in comparison to current operating and maintenance costs and the lost revenue resulting from unscheduled downtime. In most cases, the payback period is measured in months or even weeks. This paper identifies the following mechanical (nonaerodynamic) compressor upgrades and discusses the technical and commercial advantages of each, calling on actual field examples to illustrate achieved benefits: • Floating ring oil seals • Dry gas seals • Seal gas conditioning systems • Damper seals • Polymer labyrinth seals • Noise attenuatio

Design, Operation, And Maintenance Considerations For Improved Dry Gas Seal Reliability In Centrifugal Compressors.

Tutorialpg. 203-208The use of dry gas seals in process gas centrifugal compressors has increased dramatically over the last 20 years, replacing traditional oil film seals in most applications. Over 80 percent of centrifugal gas compressors manufactured today are equipped with dry gas seals. As dry gas seals have gained acceptance with users and centrifugal compressor original equipment manufacturers (OEMs), the operating envelope is continually being redefined. Ever greater demands are being placed on dry gas seals and their support systems, requiring continual improvements in the design of the dry gas seal environment, both internal and external to the compressor proper. Contamination is a leading cause of dry gas seal degradation and reduced reliability. This paper examines the experiences of one centrifugal compressor OEM in this regard. Several potential sources of dry gas seal contamination are analyzed, drawing from actual field experience, and various means of increasing dry has seal reliability are discussed

E-cadherin binds to desmoglein to facilitate desmosome assembly.

Desmosomes are adhesive junctions composed of two desmosomal cadherins: desmocollin (Dsc) and desmoglein (Dsg). Previous studies demonstrate that E-cadherin (Ecad), an adhesive protein that interacts in both trans (between opposing cells) and cis (on the same cell surface) conformations, facilitates desmosome assembly via an unknown mechanism. Here we use structure-function analysis to resolve the mechanistic roles of Ecad in desmosome formation. Using AFM force measurements, we demonstrate that Ecad interacts with isoform 2 of Dsg via a conserved Leu-175 on the Ecad cis binding interface. Super-resolution imaging reveals that Ecad is enriched in nascent desmosomes, supporting a role for Ecad in early desmosome assembly. Finally, confocal imaging demonstrates that desmosome assembly is initiated at sites of Ecad mediated adhesion, and that Ecad-L175 is required for efficient Dsg2 and desmoplakin recruitment to intercellular contacts. We propose that Ecad trans interactions at nascent cell-cell contacts initiate the recruitment of Dsg through direct cis interactions with Ecad which facilitates desmosome assembly

Signaling Dependent and Independent Mechanisms in Pemphigus Vulgaris Blister Formation

<div><p>Pemphigus vulgaris (PV) is an autoimmune epidermal blistering disease caused by autoantibodies directed against the desmosomal cadherin desmoglein-3 (Dsg3). Significant advances in our understanding of pemphigus pathomechanisms have been derived from the generation of pathogenic monoclonal Dsg3 antibodies. However, conflicting models for pemphigus pathogenicity have arisen from studies using either polyclonal PV patient IgG or monoclonal Dsg3 antibodies. In the present study, the pathogenic mechanisms of polyclonal PV IgG and monoclonal Dsg3 antibodies were directly compared. Polyclonal PV IgG cause extensive clustering and endocytosis of keratinocyte cell surface Dsg3, whereas pathogenic mouse monoclonal antibodies compromise cell-cell adhesion strength without causing these alterations in Dsg3 trafficking. Furthermore, tyrosine kinase or p38 MAPK inhibition prevents loss of keratinocyte adhesion in response to polyclonal PV IgG. In contrast, disruption of adhesion by pathogenic monoclonal antibodies is not prevented by these inhibitors either in vitro or in human skin explants. Our results reveal that the pathogenic activity of polyclonal PV IgG can be attributed to p38 MAPK-dependent clustering and endocytosis of Dsg3, whereas pathogenic monoclonal Dsg3 antibodies can function independently of this pathway. These findings have important implications for understanding pemphigus pathophysiology, and for the design of pemphigus model systems and therapeutic interventions.</p> </div