The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Ronald T. Raines - One of the best experts on this subject based on the ideXlab platform.
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Water-soluble phosphinothiols for traceless staudinger Ligation and integration with expressed protein Ligation.
Journal of the American Chemical Society, 2007Co-Authors: Annie Tam, Matthew B. Soellner, Ronald T. RainesAbstract:The traceless Staudinger Ligation is an effective means to synthesize an amide bond between two groups of otherwise orthogonal reactivity: a phosphinothioester and an azide. An important application of the Staudinger Ligation is in the Ligation of peptides at a variety of residues. Here, we demonstrate that the traceless Staudinger Ligation can be achieved in water with a water-soluble reagent. Those reagents that provide a high yield of amide product discourage protonation of the nitrogen in the key iminophosphorane intermediate. The most efficacious reagent, bis(p-dimethylaminoethyl)phosphinomethanethiol, mediates the rapid Ligation of equimolar substrates in water. This reagent is also able to perform a transthioesterification reaction with the thioester intermediate formed during intein-mediated protein splicing. Hence, the traceless Staudinger Ligation can be integrated with expressed protein Ligation, extending the reach of modern protein chemistry.
Takahiro Mimae - One of the best experts on this subject based on the ideXlab platform.
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advantage of absorbable suture material for pulmonary artery Ligation
The Japanese Journal of Thoracic and Cardiovascular Surgery, 2010Co-Authors: Tsuneo Hirayasu, Keiko B. Kimura, Yoshihiro Miyata, Takahiro Mimae, Morihito OkadaAbstract:The applicability of absorbable materials as ligatures of pulmonary vessels has not been described. The present study compares tissue reactions around sites of pulmonary arteries ligated with absorbable material (Vicryl) and with nonabsorbable material (silk). Beagle dogs underwent thoracotomy and the pulmonary artery branches were ligated with silk or Vicryl under general anesthesia. The ligated arterial tissues were obtained at 4 and 8 weeks after thoracotomy and processed for pathological analysis. The arteries ligated using Vicryl or silk were clinically completely sealed at 4 weeks after Ligation. More inflammation and granuloma were evident at tissues surrounding Ligations made with silk than with Vicryl at 8 weeks. Hyperplasia of the arterial intima continued at 8 weeks after Ligation with both Vicryl and silk sutures, although some hyperplasia similar to that in nonligated arterial intima appeared at 4 weeks after Ligation. Less inflammation and granuloma are caused at arterial tissues around Ligations accomplished with absorbable Vicryl than those done with nonabsorbable silk sutures, although both are equally effective. Absorbable sutures might be suitable for ligating pulmonary arteries.
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Advantage of absorbable suture material for pulmonary artery Ligation
General Thoracic and Cardiovascular Surgery, 2010Co-Authors: Takahiro Mimae, Tsuneo Hirayasu, Keiko B. Kimura, Yoshihiro Miyata, Morihito OkadaAbstract:Purpose The applicability of absorbable materials as ligatures of pulmonary vessels has not been described. The present study compares tissue reactions around sites of pulmonary arteries ligated with absorbable material (Vicryl) and with nonabsorbable material (silk). Methods Beagle dogs underwent thoracotomy and the pulmonary artery branches were ligated with silk or Vicryl under general anesthesia. The ligated arterial tissues were obtained at 4 and 8 weeks after thoracotomy and processed for pathological analysis. Results The arteries ligated using Vicryl or silk were clinically completely sealed at 4 weeks after Ligation. More inflammation and granuloma were evident at tissues surrounding Ligations made with silk than with Vicryl at 8 weeks. Hyperplasia of the arterial intima continued at 8 weeks after Ligation with both Vicryl and silk sutures, although some hyperplasia similar to that in nonligated arterial intima appeared at 4 weeks after Ligation. Conclusion Less inflammation and granuloma are caused at arterial tissues around Ligations accomplished with absorbable Vicryl than those done with nonabsorbable silk sutures, although both are equally effective. Absorbable sutures might be suitable for ligating pulmonary arteries.
Morihito Okada - One of the best experts on this subject based on the ideXlab platform.
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advantage of absorbable suture material for pulmonary artery Ligation
The Japanese Journal of Thoracic and Cardiovascular Surgery, 2010Co-Authors: Tsuneo Hirayasu, Keiko B. Kimura, Yoshihiro Miyata, Takahiro Mimae, Morihito OkadaAbstract:The applicability of absorbable materials as ligatures of pulmonary vessels has not been described. The present study compares tissue reactions around sites of pulmonary arteries ligated with absorbable material (Vicryl) and with nonabsorbable material (silk). Beagle dogs underwent thoracotomy and the pulmonary artery branches were ligated with silk or Vicryl under general anesthesia. The ligated arterial tissues were obtained at 4 and 8 weeks after thoracotomy and processed for pathological analysis. The arteries ligated using Vicryl or silk were clinically completely sealed at 4 weeks after Ligation. More inflammation and granuloma were evident at tissues surrounding Ligations made with silk than with Vicryl at 8 weeks. Hyperplasia of the arterial intima continued at 8 weeks after Ligation with both Vicryl and silk sutures, although some hyperplasia similar to that in nonligated arterial intima appeared at 4 weeks after Ligation. Less inflammation and granuloma are caused at arterial tissues around Ligations accomplished with absorbable Vicryl than those done with nonabsorbable silk sutures, although both are equally effective. Absorbable sutures might be suitable for ligating pulmonary arteries.
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Advantage of absorbable suture material for pulmonary artery Ligation
General Thoracic and Cardiovascular Surgery, 2010Co-Authors: Takahiro Mimae, Tsuneo Hirayasu, Keiko B. Kimura, Yoshihiro Miyata, Morihito OkadaAbstract:Purpose The applicability of absorbable materials as ligatures of pulmonary vessels has not been described. The present study compares tissue reactions around sites of pulmonary arteries ligated with absorbable material (Vicryl) and with nonabsorbable material (silk). Methods Beagle dogs underwent thoracotomy and the pulmonary artery branches were ligated with silk or Vicryl under general anesthesia. The ligated arterial tissues were obtained at 4 and 8 weeks after thoracotomy and processed for pathological analysis. Results The arteries ligated using Vicryl or silk were clinically completely sealed at 4 weeks after Ligation. More inflammation and granuloma were evident at tissues surrounding Ligations made with silk than with Vicryl at 8 weeks. Hyperplasia of the arterial intima continued at 8 weeks after Ligation with both Vicryl and silk sutures, although some hyperplasia similar to that in nonligated arterial intima appeared at 4 weeks after Ligation. Conclusion Less inflammation and granuloma are caused at arterial tissues around Ligations accomplished with absorbable Vicryl than those done with nonabsorbable silk sutures, although both are equally effective. Absorbable sutures might be suitable for ligating pulmonary arteries.
James P. Tam - One of the best experts on this subject based on the ideXlab platform.
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Butelase-mediated cyclization and Ligation of peptides and proteins
Nature Protocols, 2016Co-Authors: Giang K. T. Nguyen, Yibo Qiu, Yuan Cao, Xinya Hemu, Chuan-fa Liu, James P. TamAbstract:Enzymes that catalyze efficient macrocyclization or site-specific Ligation of peptides and proteins can enable tools for drug design and protein engineering. Here we describe a protocol to use butelase 1, a recently discovered peptide ligase, for high-efficiency cyclization and Ligation of peptides and proteins ranging in size from 10 to >200 residues. Butelase 1 is the fastest known ligase and is found in pods of the common medicinal plant Clitoria ternatea (also known as butterfly pea). It has a very simple C-terminal-specific recognition motif that requires Asn/Asp (Asx) at the P1 position and a dipeptide His–Val at the P1′ and P2′ positions. Substrates for butelase-mediated Ligation can be prepared by standard Fmoc (9-fluorenylmethyloxycarbonyl) chemistry or recombinant expression with the minimal addition of this tripeptide Asn–His–Val motif at the C terminus. Butelase 1 achieves cyclizations that are 20,000 times faster than those of sortase A, a commonly used enzyme for backbone cyclization. Unlike sortase A, butelase is traceless, and it can be used for the total synthesis of naturally occurring peptides and proteins. Furthermore, butelase 1 is also useful for intermolecular Ligations and synthesis of peptide or protein thioesters, which are versatile activated intermediates necessary for and compatible with many chemical Ligation methods. The protocol describes steps for isolation and purification of butelase 1 from plant extract using a four-step chromatography procedure, which takes ∼3 d. We then describe steps for intramolecular cyclization, intermolecular Ligation and butelase-mediated synthesis of protein thioesters. Butelase reactions are generally completed within minutes and often achieve excellent yields. This protocol from Nguyen et al . describes the use of the plant cyclase butelase 1 for the efficient cyclization and Ligation of peptides and proteins. After extraction from Clitoria ternatea , the protocol describes reactions for cyclization, Ligation and synthesis of protein thioesters.
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Butelase-mediated cyclization and Ligation of peptides and proteins.
Nature protocols, 2016Co-Authors: Giang K. T. Nguyen, Yibo Qiu, Yuan Cao, Xinya Hemu, Chuan-fa Liu, James P. TamAbstract:Enzymes that catalyze efficient macrocyclization or site-specific Ligation of peptides and proteins can enable tools for drug design and protein engineering. Here we describe a protocol to use butelase 1, a recently discovered peptide ligase, for high-efficiency cyclization and Ligation of peptides and proteins ranging in size from 10 to >200 residues. Butelase 1 is the fastest known ligase and is found in pods of the common medicinal plant Clitoria ternatea (also known as butterfly pea). It has a very simple C-terminal-specific recognition motif that requires Asn/Asp (Asx) at the P1 position and a dipeptide His-Val at the P1' and P2' positions. Substrates for butelase-mediated Ligation can be prepared by standard Fmoc (9-fluorenylmethyloxycarbonyl) chemistry or recombinant expression with the minimal addition of this tripeptide Asn-His-Val motif at the C terminus. Butelase 1 achieves cyclizations that are 20,000 times faster than those of sortase A, a commonly used enzyme for backbone cyclization. Unlike sortase A, butelase is traceless, and it can be used for the total synthesis of naturally occurring peptides and proteins. Furthermore, butelase 1 is also useful for intermolecular Ligations and synthesis of peptide or protein thioesters, which are versatile activated intermediates necessary for and compatible with many chemical Ligation methods. The protocol describes steps for isolation and purification of butelase 1 from plant extract using a four-step chromatography procedure, which takes ∼3 d. We then describe steps for intramolecular cyclization, intermolecular Ligation and butelase-mediated synthesis of protein thioesters. Butelase reactions are generally completed within minutes and often achieve excellent yields.
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Methods and strategies of peptide Ligation.
Biopolymers, 2001Co-Authors: James P. Tam, Khee Dong EomAbstract:This review focuses on the concept, methods, and strategies of orthogonal peptide Ligation. It updates our previous review in 1999 on the same subject matter in Biopolymers (Peptide Science, 1999, Vol. 51, p. 311). Orthogonal peptide Ligation is an amino terminal specific method to couple chemically unprotected peptides or proteins derived from synthetic or biosynthetic sources. Unlike conventional chemical methods, peptide Ligation methods do not require coupling reagents or protection schemes, but are achieved through a variable chemoselective capture step and then an invariable intramolecular acyl transfer reaction. It is also a convergent method with the fewest steps. More than a dozen orthogonal Ligation methods have been developed based on captures by either imine or thioester chemistries to afford native and unusual amino acids at Ligation sites of linear, branched, or cyclic peptides. The Ligation strategies for multiple segments including sequential and tandem Ligations are also discussed.
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Orthogonal segment Ligation
Peptides for the New Millennium, 1Co-Authors: Zhenwei Miao, Jin-long Yang, Kalle Kaljuste, Li Huang, James P. TamAbstract:Orthogonal Ligation is a convergent, amide-bond condensation strategy for two unprotected peptide segments regiospecific to a particular N-terminal amino acid. Conceptually, it is similar to other orthogonal strategies such as orthogonal protection, activation, and coupling used in chemistry to distinguish one functional group from another based on chemoselectivity. The ability of orthogonal Ligation methods to avoid polymerization reactions may provide a tandem Ligation scheme for coupling multiple peptide segments to further enhance the efficiency of convergent synthesis. To achieve the tandem Ligation scheme using unprotected peptide segments without any protection or deprotection step, regioselectivity is required to distinguish one Nterminal amino acid from another during the sequential Ligation steps. Over the past six years, our laboratory has developed a repertoire of orthogonal Ligation methods toward this end [1-4]. These methods are based on two types of capture mechanisms: imine [1] and thioester [2,5]. Thiaproline Ligation [1] is the first example demonstrating imine capture and the orthogonal Ligation concept (Fig. 1). In aqueous conditions, this Ligation employs an acyl segment carrying a glycoaldehyde ester 1 to capture an Nterminal (Nt) Cys segment 2a through an imine 3a, which rapidly tautomerizes to a thiazolidine ester 4a. The O-ester then rearranges to a stable amide bond, thiaproline (SPro) product 5a, at the Ligation site. The thiaproline Ligation is facile under aqueous conditions at pH 4 to 7. Although similar Ligation reactions could occur with five other Nt-amino acids, including Nt-Ser 2b, -Thr 2c, -Trp 2d, -His 2e and -Asn 2f, these N-terminal amino acids do not readily undergo imine capture reaction in aqueous solutions and occur only slowly under non-aqueous conditions. This paper describes a new reaction condition for imine Ligation with these six different N-terminal amino acids that leads to a thiaproline bond with Nt-Cys, an oxaproline bond with Nt-Ser or Nt-Thr, as well as other imidic bonds with NtTrp, Nt-His, and Nt-Asn (Fig. 1).
Susan Hartzell - One of the best experts on this subject based on the ideXlab platform.
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Erythropoietin inhibits SGK1-dependent Th17 cell induction and Th17 cell–dependent kidney disease
JCI Insight, 2019Co-Authors: Chiara Donadei, Andrea Angeletti, Chiara Cantarelli, Vivette D. D'agati, Gaetano La Manna, Enrico Fiaccadori, Julian K. Horwitz, Huabao Xiong, Chiara Guglielmo, Susan HartzellAbstract:IL-17–producing CD4+ (Th17) cells are pathogenically linked to autoimmunity and, specifically, to autoimmune kidney disease. The newly recognized immunoregulatory functions of erythropoietin (EPO) and its predominant intrarenal source suggested that EPO physiologically regulates Th17 cell differentiation, thereby serving as a barrier to development of autoimmune kidney disease. Using in vitro studies of human and murine cells and in vivo models, we show that EPO Ligation of its receptor (EPO-R) on CD4+ T cells directly inhibits Th17 cell generation and promotes transdifferentiation of Th17 cells into IL-17–FOXP3+CD4+ T cells. Mechanistically, EPO/EPO-R Ligation abrogates upregulation of SGK1 gene expression and blocks p38 activity to prevent SGK1 phosphorylation, thereby inhibiting RORC-mediated transcription of IL17 and IL23 receptor genes. In a murine model of Th17 cell–dependent aristolochic acid–induced interstitial kidney disease associated with reduced renal EPO production, we demonstrate that transgenic EPO overexpression or recombinant EPO (rEPO) administration limits Th17 cell formation and clinical/histological disease expression. EPO/EPO-R Ligations on CD4+ T cells abrogate, while absence of T cell–expressed EPO-R augments, Th17 cell induction and clinical/histological expression of pristane-induced glomerulonephritis (associated with decreased intrarenal EPO). rEPO prevents spontaneous glomerulonephritis and Th17 cell generation in MRL-lpr mice. Together, our findings indicate that EPO physiologically and therapeutically modulates Th17 cells to limit expression of Th17 cell–associated autoimmune kidney disease.
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erythropoietin inhibits sgk1 dependent th17 cell induction and th17 cell dependent kidney disease
JCI insight, 2019Co-Authors: Chiara Donadei, Andrea Angeletti, Chiara Cantarelli, Gaetano La Manna, Enrico Fiaccadori, Julian K. Horwitz, Huabao Xiong, Chiara Guglielmo, Vivette D Dagati, Susan HartzellAbstract:IL-17–producing CD4+ (Th17) cells are pathogenically linked to autoimmunity and, specifically, to autoimmune kidney disease. The newly recognized immunoregulatory functions of erythropoietin (EPO) and its predominant intrarenal source suggested that EPO physiologically regulates Th17 cell differentiation, thereby serving as a barrier to development of autoimmune kidney disease. Using in vitro studies of human and murine cells and in vivo models, we show that EPO Ligation of its receptor (EPO-R) on CD4+ T cells directly inhibits Th17 cell generation and promotes transdifferentiation of Th17 cells into IL-17–FOXP3+CD4+ T cells. Mechanistically, EPO/EPO-R Ligation abrogates upregulation of SGK1 gene expression and blocks p38 activity to prevent SGK1 phosphorylation, thereby inhibiting RORC-mediated transcription of IL17 and IL23 receptor genes. In a murine model of Th17 cell–dependent aristolochic acid–induced interstitial kidney disease associated with reduced renal EPO production, we demonstrate that transgenic EPO overexpression or recombinant EPO (rEPO) administration limits Th17 cell formation and clinical/histological disease expression. EPO/EPO-R Ligations on CD4+ T cells abrogate, while absence of T cell–expressed EPO-R augments, Th17 cell induction and clinical/histological expression of pristane-induced glomerulonephritis (associated with decreased intrarenal EPO). rEPO prevents spontaneous glomerulonephritis and Th17 cell generation in MRL-lpr mice. Together, our findings indicate that EPO physiologically and therapeutically modulates Th17 cells to limit expression of Th17 cell–associated autoimmune kidney disease.
