CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2007
Craig Steven McLachlan
SUMMARY 1The aim of the present study was to examine, in the dog myocardium, the incidence of zig-zag mitochondrial cristae over time in the non-ischaemic posterior wall, following an acute anterior wall infarct. 2Changes within the myocardial mitochondrial crista membrane in dogs were investigated following acute left anterior descending coronary artery ligation. Transmyocardial biopsy samples were taken serially from the posterior non-ischaemic wall in the same dog. Changes in heart mitochondrial cristae were examined by transmission electron microscopy prior to coronary ligation (control) and 40 min and 2, 4, 6 and 24 h postinfarction. 3In control hearts, 90% of mitochondrial cristae had a lamelliform appearance. Following infarction, there were twotransitional states with respect to mitochondrial cristae, the first characterized by undulating lamelliform cristae that are also found in 10% of control samples and a second transitional state that was zig-zag and reached a maximum between 6 and 24 h after infarction. 4In conclusion, an undulating lamelliform crista pattern is present in the non-ischaemic wall of the acute infarcted dog and we hypothesize that this may be an intermediate from, between ,normal' lamelliform and ,abnormal' zig-zag cristae. [source]

Coronary Recanalization Due to Presumed Thrombosis Following Surgical Ligation of a Large Right Coronary Artery to Right Ventricle Fistula

CONGENITAL HEART DISEASE, Issue 4 2008
John T. Fahey MD
ABSTRACT We report angiographic findings in an infant with congestive heart failure due to a large right coronary artery to right ventricular fistula who underwent surgical ligation. Repeat catheterization 2 years later unexpectedly showed extensive thrombosis of the right coronary artery with multiple recanalized channels supplying the right coronary distribution. Review of the literature showed that this may not be an uncommon finding. [source]

Successful Endoscopic Band Ligation for Treatment of Postpolypectomy Hemorrhage

DIGESTIVE ENDOSCOPY, Issue 4 2000
Yohei Mizuta
We describe a case of large pedunculated tubulovillous adenoma of the stomach associated with postpolypectomy hemorrhage, which was successfully treated by endoscopic band ligation. The case study involved a 60-year-old Japanese woman with a pedunculated polyp with a slightly lobular surface, measuring 25 mm in diameter. It was detected on the posterior wall of the middle body of the gastric remnant. The lesion was diagnosed as a tubulovillous adenoma by a biopsy specimen and treated by endoscopic polypectomy using the detachable snare to prevent postpolypectomy hemorrhage. There was no episode of immediate postpolypectomy hemorrhage, but hematemesis occured 18 h after the excision. Endoscopic examination of the stomach showed the mark left by bleeding on the cutting surface and the absence of the detachable snare. Endoscopic intervention by rubber band ligation was performed to prevent the recurrent bleeding. Complete hemostasis was obtained and no serious complications occured. [source]

IL-12 and IL-18 down-regulate B cell migration in an Ly49D-dependent manner

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 7 2007
Gili Hart
Abstract In order to complete their maturation and participate in the humoral immune response, immature B cells that leave the bone marrow are targeted to specific areas in the spleen, where they differentiate into mature cells. Previously, we showed that immature B cells actively down-regulate their integrin-mediated migration to LN or to sites of inflammation, enabling their targeting to the spleen. This inhibition is mediated by IFN-,, which is transcribed and secreted at low levels by these immature B cells; its expression is subsequently down-regulated following B cell maturation. The activating and inhibitory MHC class,I receptors, Ly49D and Ly49G2, regulate IFN-, secretion in B cells, preventing their migration to antigen-enriched sites and their premature encounter with an antigen, while enabling their entry into the LN when mature. In the present study, we elucidate the pathways by which the Ly49 receptors regulate IFN-, levels. We show that Ly49D stimulation triggers a signaling cascade that increases transcription of both IL-12B and IL-18; these, in turn, can interact with their specific receptors, which are expressed at elevated levels on immature B cells. Ligation of the IL-12B and IL-18 receptors induces the secretion of IFN-,, thereby regulating their cytoskeleton rearrangement and migration. [source]

The Role of Axial Ligation in Nitrate Reductase: A Model Study by DFT Calculations on the Mechanism of Nitrate Reduction

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 34 2008
Kuntal Pal
Abstract The reactivity differences of the model anionic complexes [Mo(mnt)2(X)(PPh3)], [mnt2, = 1,2-dicyanoethylenedithiolate; X = SPh (1a), SEt (1b), Cl (1c), Br (1b)] towards oxygen atom transfer from nitrate, which is a key step performed by nitrate reductase, has been investigated by density functional theory calculations. Unlike complexes 1a and 1b, complexes 1c and 1d do not react with nitrate. Thermodynamically, all these complexes have a similar ability to generate the pentacoordinate active state [Mo(mnt)2(X)], by dissociation of PPh3, although the inaccessibility of the dxy orbital in 1c,d and the instability of the corresponding nitrate-bound enzyme substrate (ES) type complex contributes to their failure to reduce nitrate. The nature of the ES complex for 1a,b is described. The variation in the experimental data due to the change of axial ligation from SPh to SEt on the catalytic pathway has also been addressed. The gas-phase and solvent-corrected potential energy surface for the reaction of 1a,b with nitrate are established with fully optimized minima and transition states.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Coenzyme B12 Model Studies , Kinetics of Axial Ligation of Alkylcobalt Complexes Containing a Tridentate Amino-Oximate Ligand

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2003
Basam M. Alzoubi
Abstract The ligand-substitution reaction of [RCo(LNHpy)(HLNHpy)]+ by cyanide was studied in methanol as a solvent, where R = Et (1), Me (2), CF3CH2 (3), and bridging CH2 (4), HLNHpy = 2-(2-pyridylethyl)amino-3-butanone oxime and LNHpy, is its conjugate base. The second-order rate constants for the substitution of the 2-pyridylethyl moiety in [RCo(LNHpy)(HLNHpy)]+ by cyanide were found to be 19.1, 0.25, 2.2·10,2, and 1.7·10,2M,1·s,1 for R = Et, Me, CF3CH2, and bridging CH2, respectively. From the temperature- and pressure-dependence studies of the substitution reaction, the activation parameters (,H,, ,S,, ,V,) for the reaction of [RCo(LNHpy)(HLNHpy)]+ with cyanide in methanol were found to be, for R = Et: 69±2 kJ·mol,1, +11±7 J·K,1 mol,1, +9.6±0.3 cm3·mol,1; R = Me: 86±4 kJ·mol,1, +31±15 J·K,1·mol,1, +4.3±0.2 cm3·mol,1; R = CF3CH2: 73±3 kJ·mol,1, ,33±10 J·K,1·mol,1, +8.7±0.2 cm3·mol,1; R = bridging CH2: 80±1 kJ·mol,1, ,13±3 J·K,1·mol,1, +5.4±0.1 cm3·mol,1, respectively. Based on the reported rate and activation parameters, the mechanism of the ligand-substitution reaction varies between a limiting dissociative and a dissociative interchange type of mechanism depending on the ,-donor and steric effects of the alkyl group. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Hybrid Bioorganic,Inorganic Materials Prepared by Site-Specific Ligation of Peptides to Functionalized Polydisperse Silica Particles

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2005
Pascal Joly
Abstract We describe the synthesis of semicarbazide- or glyoxylyl-functionalized polydisperse silica particles and their use for the preparation of hybrid polypeptide,silica materials. The peptides were attached to the surface of functionalized silicas by site-specific ,-oxo hydrazone or semicarbazone ligation. The reaction of semicarbazide silicas with a model glyoxylyl peptide was found to be very efficient under stoichiometric conditions and led to ligation yields of about 90,%. The use of glyoxylyl silicas and of hydrazinoacetyl peptides led to lower yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Synthesis of Peptide-PNA-Peptide Conjugates by Semi-Solid-Phase Chemical Ligation Combined with Deactivation/Capture of Excess Reactants

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2004
Martijn C. de Koning
Abstract An expeditious route to peptide-PNA-peptide conjugates following a two-step native chemical ligation (NCL) strategy is described. A cys-PNA-thioester is immobilized on PEGA-aldehyde resin by thiazolidine formation, followed by capping of excess resin aldehydes. The first NCL reaction is then performed with the immobilized PNA-thioester, to give, after release from the solid support, the cys-PNA-peptide intermediate with relatively high purity. The latter is then converted into the target compound by the second NCL reaction with a thioester peptide, the excess of which is captured using a cysteine-PEGA resin. The resulting peptide-PNA-peptide can then be readily isolated by a simple purification step. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Tuning the Energy Level and Photophysical and Electroluminescent Properties of Heavy Metal Complexes by Controlling the Ligation of the Metal with the Carbon of the Carbazole Unit,

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2007
L. Yang
Abstract Four novel IrIII and PtII complexes with cyclometalated ligands bearing a carbazole framework are prepared and characterized by elemental analysis, NMR spectroscopy, and mass spectrometry. Single-crystal X-ray diffraction studies of complexes 1, 3, and 4 reveal that the 3- or 2-position C atom of the carbazole unit coordinates to the metal center. The difference in the ligation position results in significant shifts in the emission spectra with the changes in wavelength being 84,nm for the Ir complexes and 63,nm for the Pt complexes. The electrochemical behavior and photophysical properties of the complexes are investigated, and correlate well with the results of density functional theory (DFT) calculations. Electroluminescent devices with a configuration of ITO/NPB/CBP:dopant/BCP/AlQ3/LiF/Al can attain very high efficiencies. [source]

The PI-3 kinase/Akt pathway and T cell activation: pleiotropic pathways downstream of PIP3

IMMUNOLOGICAL REVIEWS, Issue 1 2003
Lawrence P. Kane
Summary Ligation of the T cell receptor for antigen (TCR) and/or costimulatory receptor CD28 results in rapid activation of phosphoinositide-3 kinase (PI-3 kinase). It remains unclear, however, precisely how this activation occurs and also how the newly generated phospholipid products trigger the various events associated with T cell activation. Here we discuss the current understanding of how PI-3 kinase is activated by the TCR and CD28 and what roles its products play in T cell activation. We also review recent advances in understanding the function of Akt in particular, especially its role in CD28 costimulation. Several functional targets of Akt are discussed in this regard: inducible transcription, cell survival, glucose metabolism, and the cellular translational machinery. These pathways have been associated with TCR/CD28 costimulation, and they have also been implicated as targets of Akt. [source]

Ionizing radiation as a response-enhancing agent for CD95-mediated apoptosis

INTERNATIONAL JOURNAL OF CANCER, Issue 4 2001
Michael A. Sheard Ph.D.
Abstract CD95 (Fas/APO-1) is a death receptor on the surface of a wide variety of cell types. In most cells examined, ionizing radiation acts as a response-enhancing agent for CD95-mediated cell death. Although DNA-damaging radiation appears to modulate CD95-mediated signals through multiple mechanisms, the only well-characterized mechanism is activation of the tumor-suppressor protein p53, which transcriptionally regulates the expression of CD95 on various cell types. The ligand for CD95 is expressed by activated lymphocytes and natural-killer cells, which produce factors that sensitize cells resistant to CD95-mediated cell death. Ligation of CD95 on irradiated tumor cells might be achievable using emerging modalities that reactivate the stalled anti-tumor immune response. © 2001 Wiley-Liss, Inc. [source]

Ischemic Preconditioning: Fact or Fantasy?

JOURNAL OF CARDIAC SURGERY, Issue 6 2002
Christopher D. Raeburn M.D.
In the ensuing years, surgeons have learned to discriminate a biochemical/metabolic/functional spectrum of cardiac states ranging from healthy myocardium to "stunned" or "hibernating" heart to the modes of "apoptotic" or "necrotic" cardiomyocyte death. It is now clear that "protective cardiac preconditioning" influences all of these cardiac states. The cellular mechanisms of preconditioning (PC) are now sufficiently understood to permit clinical application. Ligation of adrenergic, adenosine, bradykinin or opioid receptors involves signaling via both tyrosine and calcium-dependent protein kinases (PKC), which activate mitochondrial ATP-dependent potassium channels. Subsequently, the release of oxygen radicals induces nuclear translocation of transcriptional regulators, which transform the cardiomyocyte into a more resilient cell. Although preconditioning was initially recognized as protecting only against infarction, PC also limits postischemic dysrhythmias and enhances contractile function. Phase I (safety) and phase II (efficacy) clinical trials now persuasively support pharmacological preconditioning as a safe mode of preventing postcardiac surgical complications. Indeed, preconditioning is currently being proposed as adjunctive to hypothermic perfusates in protecting against the obligate organ ischemia during transplantation. [source]

5-aminoisoquinolin-1(2H)-one, a water-soluble poly (ADP-ribose) polymerase (PARP) inhibitor reduces the evolution of experimental periodontitis in rats

JOURNAL OF CLINICAL PERIODONTOLOGY, Issue 2 2007
Rosanna Di Paola
Abstract Background: Poly (ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the tissue injury associated with ischaemia-reperfusion and inflammation. Recent studies have demonstrated that PARP activation plays a crucial role in the pathogenesis of acute periodontal injury. Aim: We have investigated the effect of 5-aminoisoquinolin-1(2H)-one (5-AIQ), a water-soluble PARP inhibitor, in a rat model of periodontitis. Materials and Methods: Periodontitis was induced in rats by placing a 2/0 braided silk ligature around the lower left first molar. At day eight, the gingivomucosal tissue encircling the mandibular first molar was removed for biochemical and histological analysis. Results and Conclusions: Ligation significantly induced an increased neutrophil infiltration and a positive staining for PARP activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone destruction. Intraperitonial injection of 5-aminoisoquinolin-1(2H)-one (5-AIQ) (5 mg/kg daily for eight days) significantly decreased all of the parameters of inflammation as described above. This suggests that inhibition of PARP may represent a novel approach for the treatment of periodontal disease. [source]

Influence of subcutaneous administration of recombinant TNF-, on ligature-induced periodontitis in rats

JOURNAL OF PERIODONTAL RESEARCH, Issue 2 2003
Rok Ga
Proinflammatory cytokine tumor necrosis factor alpha (TNF-,) was found in inflamed periodontal tissues and many studies pointed to its significant role in development of periodontal disease. In this study, the influence of subcutaneously administered recombinant human TNF-, (rhTNF-,) on inflammatory reaction and periodontal breakdown in rats was analyzed during experimental periodontitis, induced by placing silk ligatures around the maxillary right second molar tooth. The rats were divided into two groups with five animals in each; the first group was infused subcutaneously with rhTNF-, via osmotic pumps for 2 weeks and the second group was infused with phosphate-buffered saline (PBS) in the same manner. Inflammatory reaction and periodontal breakdown was evaluated morphometrically on hematoxylin and eosin stained sections. Serum ionized calcium and inorganic phosphates were monitored colorimetrically. Serum calcium and phosphate levels were similar in rats receiving rhTNF-, and PBS. Ligation resulted in accelerated periodontal breakdown, while subcutaneous rhTNF-, administration by itself had no significant effect. Combined effect of subcutaneous rhTNF-, administration and ligation resulted in a significantly greater inflammatory reaction and periodontal breakdown then either treatment alone. We concluded that the subcutaneous administration of rhTNF-, accelerates the progression of experimental periodontitis in rats. [source]

B7-H1 expression is upregulated in peripheral blood CD14+ monocytes of patients with chronic hepatitis B virus infection, which correlates with higher serum IL-10 levels

JOURNAL OF VIRAL HEPATITIS, Issue 11 2006
L. Geng
Summary., Chronicity in hepatitis B virus (HBV) infection is maintained by increased type 2 T-helper cell response, possibly because of increased interleukin-10 (IL-10) productions. B7-H1 can negatively regulate T-cell responses via its receptor, programmed death 1. Ligation of B7-H1 to T-cells can result in the preferential secretion of IL-10. In this study, we investigated whether there was an upregulated expression of B7-H1 in peripheral blood mononuclear cells in patients chronically infected by HBV and further explored the correlation between B7-H1 expression and serum interleukin 2, interferon- ,, IL-10, HBeAg, alanine aminotransferase (ALT) levels and viral load. Fifty-five patients with chronic HBV infection and 20 healthy controls (HCs) were enrolled in the present study. The results showed that in patients with chronic hepatitis B CD14+ monocytes but not CD3+ and CD19+ cells had a significantly increased expression of B7-H1 compared with HCs, which positively correlates with serum IL-10 levels and the presence of HBeAg and negatively correlates with serum ALT levels. In conclusion, chronic HBV patients harbour an increased B7-H1 expression in CD14+ monocytes compared with controls, which may be responsible for the increased serum IL-10 levels. This might be an important way by which HBV evades an adequate immune response, leading to viral persistence and disease chronicity. [source]

Collateral Capillary Arterialization following Arteriolar Ligation in Murine Skeletal Muscle

MICROCIRCULATION, Issue 5 2010
FEILIM MAC GABHANN
Microcirculation (2010) 17, 333,347. doi: 10.1111/j.1549-8719.2010.00034.x Abstract Objective:, Chronic and acute ischemic diseases,peripheral artery disease, coronary artery disease, stroke,result in tissue damage unless blood flow is maintained or restored in a timely manner. Mice of different strains recover from arteriolar ligation (by increasing collateral blood flow) at different speeds. We quantify the spatio-temporal patterns of microvascular network remodeling following arteriolar ligation in different mouse strains to better understand inter-individual variability. Methods:, Whole-muscle spinotrapezius microvascular networks of mouse strains C57Bl/6, Balb/c and CD1 were imaged using confocal microscopy following ligation of feeding arterioles. Results:, Baseline arteriolar structures of C57Bl/6 and Balb/c mice feature heavily ramified arcades and unconnected dendritic trees, respectively. This network angioarchitecture identifies ischemia-protected and ischemia-vulnerable tissues; unlike C57Bl/6, downstream capillary perfusion in Balb/c spinotrapezius is lost following ligation. Perfusion recovery requires arterialization (expansion and investment of mural cells) of a subset of capillaries forming a new low-resistance collateral pathway between arteriolar trees. Outbred CD1 exhibit either Balb/c-like or C57Bl/6-like spinotrapezius angioarchitecture, predictive of response to arteriolar ligation. Conclusions:, This collateral capillary arterialization process may explain the reported longer time required for blood flow recovery in Balb/c hindlimb ischemia, as low-resistance blood flow pathways along capillary conduits must be formed ("arterialization") before reperfusion. [source]

Traceless Ligation of Cysteine Peptides Using Selective Deselenization,

ANGEWANDTE CHEMIE, Issue 39 2010
Dr. Norman Metanis
Selektive Deselenierung: Der nativen chemischen Ligation an Selenocystein schließt sich eine selektive Deselenierung des Selenocysteins zu Alanin an , und dies in Gegenwart von ungeschützten Cysteinresten (siehe Schema). Diese Selektivität wird durch die Verwendung von wasserlöslichem Tris(2-carboxyethyl)phosphan (TCEP) in Abwesenheit eines Radikalstarters erreicht. [source]

The Mercaptomethyl Group Facilitates an Efficient One-Pot Ligation at Xaa-Ser/Thr for (Glyco)peptide Synthesis,

ANGEWANDTE CHEMIE, Issue 31 2010
Hironobu Hojo Prof.
Erleichterte Kupplung: Eine Mercaptomethylgruppe in der Seitenkette von Serin und Threonin erleichterte die native chemische Ligation an der Xaa-Ser/Thr-Position (siehe Schema; R=H, Me). Der intermediäre Thioester geht eine S-N-Acylverschiebung ein, und nach der Ligation wurde die Methylgruppe spontan abgespalten, wobei das Glycopeptid Contulakin-G und humanes Calcitonin erhalten wurden. [source]

Direct Detection of Oxygen Ligation to the Mn4Ca Cluster of Photosystem II by X-ray Emission Spectroscopy,

ANGEWANDTE CHEMIE, Issue 4 2010
Yulia Pushkar Dr.
O im Blick: Mn-K,2,5 - und -K,,,-Emissionsspektren entstehen durch Übergänge von den Ligand-2s- und -2p-Schalen der Metallkomplexe in die 1s-Metallniveaus. Auf diese Weise konnten die O-Liganden des Mn4Ca-Clusters untersucht werden, der die photosynthetische Wasserspaltung katalysiert, was erstmals den direkten Nachweis der verbrückenden Oxogruppen an Mn ermöglichte. [source]

A Pyrrolysine Analogue for Site-Specific Protein Ubiquitination,

ANGEWANDTE CHEMIE, Issue 48 2009
Xin Li
Die Kunst des Proteinnähens: D -Cys-,-Lys und sein Diastereomer L -Cys-,-Lys lesen durch das UAG-Codon (siehe Schema). Da die gebildeten Proteine in der nativen chemischen Ligation (NCL) eingesetzt werden können, sind so Proteine zugänglich, die chemoselektiv durch eine Peptidseitenkette an der ,-Position eines rational gewählten Lysinrests modifiziert (z.,B. ubiquitinyliert) sind. [source]

Ligation of the caudal mesenteric artery during resection and anastomosis of the colorectal junction for annular adenocarcinoma in two dogs

AUSTRALIAN VETERINARY JOURNAL, Issue 9 2009
SK Sarathchandra
An 8-year-old terrier cross and a 10-year-old German Shorthaired Pointer presented to the University Veterinary Centre, Sydney, for investigation of long-standing tenesmus and dyschezia. Both patients had an annular adenocarcinoma at the colorectal junction. Exploratory laparotomy was performed and the affected large intestinal segment was removed by resection and anastomosis. In both dogs, the caudal mesenteric artery was intimately associated with the mass, necessitating its ligation and transection. Postoperatively, there was no evidence of anastomosis breakdown in either case and both animals recovered well from surgery. The dogs were euthanased 8 and 10 months, respectively, after surgery because of clinical signs relating to metastatic disease. [source]

Late complications after ligation and bypass for popliteal aneurysm,

BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 2 2004
U. J. Kirkpatrick
Background: Ligation and bypass is standard treatment for popliteal aneurysm. This technique does not abolish collateral circulation to the aneurysm, which may continue to expand and/or rupture. This study assessed whether complete thrombosis of the aneurysm sac occurs after operation and examined the long-term clinical outcome. Methods: The records of all patients who underwent popliteal aneurysm repair in a university hospital over 10 years were reviewed. Patients who had undergone ligation and bypass were recalled for clinical and ultrasonographic examination to determine the fate of the aneurysm sac. Results: Persistent blood flow in the aneurysm sac was present in 12 of 36 legs a median of 48 months after operation. This was associated with symptomatic enlargement of the aneurysm in six patients. The incidence of sac enlargement was lower in bypassed aneurysms with no intrasac flow on duplex examination. Conclusion: Ligation and bypass does not always abolish blood flow in the sac of a popliteal aneurysm. It may be associated with continued expansion and late complications. Copyright © 2003 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source]

Protein Synthesis Assisted by Native Chemical Ligation at Leucine

CHEMBIOCHEM, Issue 9 2010
Ziv Harpaz
Triggering leucine: A new ligation strategy of using ,-mercaptoleucine coupled with desulfurization at leucine sites was developed, and its applicability in protein synthesis is presented. The efficiency of our Leu-NCL was examined in several model peptides and utilized for the first total synthesis of HIV-1 Tat protein. [source]

Chemical Protein Synthesis by Kinetically Controlled Ligation of Peptide O-Esters

CHEMBIOCHEM, Issue 4 2010
Ji-Shen Zheng
Designer peptides: A large reactivity difference was observed between two peptide O-esters that can undergo peptide ligation through an in situ O-to-S acyl shift. This observation allowed for the design of "one-pot" N-to-C sequential peptide fragment condensation through kinetically controlled ligation with more readily accessible peptide O-esters. [source]

Sortase-Mediated Ligation: A Gift from Gram-Positive Bacteria to Protein Engineering

CHEMBIOCHEM, Issue 5 2009
Shinya Tsukiji Dr.
Abstract A new enzymatic protein ligation tool, sortase, has recently emerged from Gram-positive bacteria. This article outlines the technique, sortase-mediated ligation, and its applications in protein engineering, which include the introduction of unnatural molecules into proteins, protein immobilization, protein,protein conjugation, protein cyclization, as a self-cleavable tag for protein expression, protein,PNA hybrids, neoglycoconjugates, and cell-surface protein labeling, etc. [source]

Synthesis and Reactivity of 6,7-dihydrogeranylazides: Reagents for Primary Azide Incorporation into Peptides and Subsequent Staudinger Ligation

CHEMICAL BIOLOGY & DRUG DESIGN, Issue 2 2006
Juhua Xu
Protein farnesyltransferase (PFTase) catalyzes the attachment of a geranylazide moiety to a peptide substrate, N -dansyl-GCVIA. Because geranylazide is actually a mixture of isomeric, interconverting primary and secondary azides, incorporation of this isoprenoid into peptides can potentially result in a corresponding mixture of prenylated peptides. Here, we first examined the reactivity of geranyl azide in a model Staudinger reaction and determined that a mixture of products is formed. We then describe the synthesis of 6,7-dihydrogeranylazide diphosphate and demonstrate that this compound allows exclusive incorporation of a primary azide into a peptide. The resulting azide-containing peptide was derivatized with a triphenylphosphine-based reagent to generate an O -alkyl imidate-linked product. Finally, we show, using a series of model reactions, that the Staudinger ligation frequently produces small amounts of O -alkyl imidate products in addition to the major amide-linked products. Thus, the alkoxyimidates we have observed as the exclusive products in the reactions of peptides containing prenylated azides also appear to be a common type of product formed using other azide-containing reactants, although at greatly reduced levels. This method for chemical modification of the C-terminus of a protein should be useful for a variety of applications in protein chemistry. [source]

ChemInform Abstract: Catalytic Staudinger,Vilarrasa Reaction for the Direct Ligation of Carboxylic Acids and Azides.

CHEMINFORM, Issue 30 2009
Jordi Bures
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: An Efficient Approach for Immobilizing the Oxo-Vanadium Schiff Base onto Polymer Supports Using Staudinger Ligation.

CHEMINFORM, Issue 43 2008
Suman L. Jain
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Direct Deprotected Glycosyl,Asparagine Ligation.

CHEMINFORM, Issue 31 2006
Katie J. Doores
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Controlling Peptide Structure with Coordination Chemistry: Robust and Reversible Peptide,Dirhodium Ligation

CHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2009
Alexander
Mild and reversible: A dirhodium tetracarboxylate reacts with peptides to bridge carboxylate side chains (see scheme). The ligation proceeds under mild aqueous conditions and is readily reversible. Dirhodium adduct formation can be used to control the conformation and supramolecular structure of peptides. [source]