1
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Li B, Yuan D, Chen H, Wang X, Liang Y, Wong CTT, Xia J. Site-selective antibody-lipid conjugates for surface functionalization of red blood cells and targeted drug delivery. J Control Release 2024; 370:302-309. [PMID: 38663752 DOI: 10.1016/j.jconrel.2024.04.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Revised: 03/23/2024] [Accepted: 04/23/2024] [Indexed: 05/04/2024]
Abstract
Displaying antibodies on carrier surfaces facilitates precise targeting and delivery of drugs to diseased cells. Here, we report the synthesis of antibody-lipid conjugates (ALCs) through site-selective acetylation of Lys 248 in human Immunoglobulin G (IgG) and the development of antibody-functionalized red blood cells (immunoRBC) for targeted drug delivery. ImmunoRBC with the HER2-selective antibody trastuzumab displayed on the surface (called Tras-RBC) was constructed following a three-step procedure. First, a peptide-guided, proximity-induced reaction transferred an azidoacetyl group to the ε-amino group of Lys 248 in the Fc domain. Second, the azide-modified IgG was subsequently conjugated with dibenzocyclooctyne (DBCO)-functionalized lipids via strain-promoted azide-alkyne cycloaddition (SPAAC) to result in ALCs. Third, the lipid portion of ALCs was then inserted into the cell membranes, and IgGs were displayed on red blood cells (RBCs) to construct immunoRBCs. We then loaded Tras-RBC with a photosensitizer (PS), Zinc phthalocyanine (ZnPc), to selectively target HER2-overexpressing cells, release ZnPc into cancer cells following photolysis, and induce photodynamic cytotoxicity in the cancer cells. This work showcases assembling immunoRBCs following site-selective lipid conjugation on therapeutic antibodies and the targeted introduction of PS into cancer cells. This method could apply to the surface functionalization of other membrane-bound vesicles or lipid nanoparticles for antibody-directed drug delivery.
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Affiliation(s)
- Biquan Li
- Department of Chemistry and Center for Cell & Developmental Biology, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | - Dingdong Yuan
- Department of Chemistry and Center for Cell & Developmental Biology, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | - Hongfei Chen
- Department of Chemistry and Center for Cell & Developmental Biology, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | - Xun Wang
- Department of Chemistry and Center for Cell & Developmental Biology, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | - Yujie Liang
- Department of Chemistry and Center for Cell & Developmental Biology, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | - Clarence T T Wong
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China.
| | - Jiang Xia
- Department of Chemistry and Center for Cell & Developmental Biology, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
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2
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Chu JH, Xiong J, Wong CTT, Wang S, Tam DY, García-Fernández A, Martínez-Máñez R, Ng DKP. Detection and Elimination of Senescent Cells with a Self-Assembled Senescence-Associated β-Galactosidase-Activatable Nanophotosensitizer. J Med Chem 2024; 67:234-244. [PMID: 38113190 PMCID: PMC10788907 DOI: 10.1021/acs.jmedchem.3c01306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 11/28/2023] [Accepted: 11/29/2023] [Indexed: 12/21/2023]
Abstract
Senescent cells have become an important therapeutic target for many age-related dysfunctions and diseases. We report herein a novel nanophotosensitizing system that is responsive to the senescence-associated β-galactosidase (β-gal) for selective detection and elimination of these cells. It involves a dimeric zinc(II) phthalocyanine linked to a β-galactose unit via a self-immolative linker. This compound can self-assemble in aqueous media, forming stable nanoscale particles in which the phthalocyanine units are stacked and self-quenched for fluorescence emission and singlet oxygen production. Upon internalization into senescent HeLa cells, these nanoparticles interact with the overproduced senescence-associated β-gal inside the cells to trigger the disassembly process through enzymatic cleavage of the glycosidic bonds, followed by self-immolation to release the photoactive monomeric phthalocyanine units. These senescent cells can then be lit up with fluorescence and eliminated through the photodynamic action upon light irradiation with a half-maximal inhibitory concentration of 0.06 μM.
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Affiliation(s)
- Jacky
C. H. Chu
- Department
of Chemistry, The Chinese University of
Hong Kong, Shatin, N.T., Hong Kong, China
| | - Junlong Xiong
- Department
of Chemistry, The Chinese University of
Hong Kong, Shatin, N.T., Hong Kong, China
- Department
of Pharmacy, The Affiliated Luohu Hospital
of Shenzhen University, Shenzhen University, Shenzhen 518001, China
| | - Clarence T. T. Wong
- Department
of Chemistry, The Chinese University of
Hong Kong, Shatin, N.T., Hong Kong, China
- Department
of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China
| | - Shuai Wang
- Department
of Chemistry, The Chinese University of
Hong Kong, Shatin, N.T., Hong Kong, China
| | - Dick Yan Tam
- Department
of Chemistry, The Chinese University of
Hong Kong, Shatin, N.T., Hong Kong, China
| | - Alba García-Fernández
- Instituto
Interuniversitario de Investigación de Reconocimiento, Molecular
y Desarrollo Tecnológico, Universitat
Politècnica de València, Universitat de València, Valencia46022, Spain
- CIBER
de Bioingeniería, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, Madrid 28029, Spain
- Unidad Mixta
UPV-CIPF de Investigación en Mecanismos de Enfermedades y Nanomedicina,
Centro de Investigación Príncipe Felipe, Universitat Politècnica de València, Valencia46012, Spain
| | - Ramón Martínez-Máñez
- Instituto
Interuniversitario de Investigación de Reconocimiento, Molecular
y Desarrollo Tecnológico, Universitat
Politècnica de València, Universitat de València, Valencia46022, Spain
- CIBER
de Bioingeniería, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, Madrid 28029, Spain
- Unidad Mixta
UPV-CIPF de Investigación en Mecanismos de Enfermedades y Nanomedicina,
Centro de Investigación Príncipe Felipe, Universitat Politècnica de València, Valencia46012, Spain
- Unidad
Mixta de Investigación en Nanomedicina y Sensores, Instituto
de Investigación Sanitaria La Fe (IIS La Fe), Universitat Politècnica e València, Valencia 46026, Spain
| | - Dennis K. P. Ng
- Department
of Chemistry, The Chinese University of
Hong Kong, Shatin, N.T., Hong Kong, China
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3
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Tang B, Lau KM, Zhu Y, Shao C, Wong WT, Chow LMC, Wong CTT. Chemical Modification of Cytochrome C for Acid-Responsive Intracellular Apoptotic Protein Delivery for Cancer Eradication. Pharmaceutics 2024; 16:71. [PMID: 38258082 PMCID: PMC10819283 DOI: 10.3390/pharmaceutics16010071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/29/2023] [Accepted: 12/30/2023] [Indexed: 01/24/2024] Open
Abstract
Delivering bioactive proteins into cells without carriers presents significant challenges in biomedical applications due to limited cell membrane permeability and the need for targeted delivery. Here, we introduce a novel carrier-free method that addresses these challenges by chemically modifying proteins with an acid-responsive cell-penetrating peptide (CPP) for selective intracellular delivery within tumours. Cytochrome C, a protein known for inducing apoptosis, served as a model for intracellular delivery of therapeutic proteins for cancer treatment. The CPP was protected with 2,3-dimethyl maleic anhydride (DMA) and chemically conjugated onto the protein surface, creating an acid-responsive protein delivery system. In the acidic tumour microenvironment, DMA deprotects and exposes the positively charged CPP, enabling membrane penetration. Both in vitro and in vivo assays validated the pH-dependent shielding mechanism, demonstrating the modified cytochrome C could induce apoptosis in cancer cells in a pH-selective manner. These findings provide a promising new approach for carrier-free and tumour-targeted intracellular delivery of therapeutic proteins for a wide range of potential applications.
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Affiliation(s)
| | | | | | | | | | - Larry M. C. Chow
- State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Kowloon, Hong Kong, China; (B.T.); (K.M.L.); (Y.Z.); (C.S.); (W.-T.W.)
| | - Clarence T. T. Wong
- State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Kowloon, Hong Kong, China; (B.T.); (K.M.L.); (Y.Z.); (C.S.); (W.-T.W.)
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4
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Wu H, Shi X, Zang Y, Zhao X, Liu X, Wang W, Shi W, Wong CTT, Sheng L, Chen X, Zhang S. 7-hydroxycoumarin-β-D-glucuronide protects against cisplatin-induced acute kidney injury via inhibiting p38MAPK-mediated apoptosis in mice. Life Sci 2023; 327:121864. [PMID: 37336359 DOI: 10.1016/j.lfs.2023.121864] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 06/03/2023] [Accepted: 06/12/2023] [Indexed: 06/21/2023]
Abstract
AIMS Cisplatin is a widely-used drug in the clinical treatment of tumors, but kidney nephrotoxicity is one of the reasons that limits its widespread use. We previously found that 7-hydroxycoumarin-β-D-glucuronide (7-HCG) was one of metabolites of skimmin and highly enriched in the kidneys and maintained a high blood concentration in skimmin-treated rats. Therefore, we investigated whether 7-HCG has a protective effect on cisplatin-induced acute kidney injury. MATERIALS AND METHODS Male C57BL/6 mice were continuously administered 7-HCG for five days, and on the third day, an intraperitoneal injection of cisplatin was given to induce acute kidney injury. After 72 h, the mice were sacrificed for analysis. Serum and renal tissue were collected for renal function evaluation. RNA sequencing was used to explore mechanism, and further validated by western blot and immunohistochemistry. In addition, pharmacokinetic study of oral 7-HCG administration was performed to examine how much 7-hydroxycoumarin (7-HC) was metabolized and 7-HC possible effect on renal protection. KEY FINDINGS 7-HCG significantly reduced serum BUN and SCR levels, and alleviated pathological damage in renal tissue, and reduced the renal index. RNA sequencing revealed that 7-HCG could reverse p38 MAPK regulation and apoptosis. By western blotting, it was found that 7-HCG could reduce renal injury by reducing p-p38, p-ERK, p-JNK, cleaved-caspase3 and Bax. The immunohistochemical results of cleaved-caspase3 were consistent with western blotting. 7-HCG also significantly reduced the production of ROS in kidney tissue. Pharmacokinetic experiments have shown that 7-HCG in the blood increased rapidly and was eliminated slowly, with an average t1/2β of 18.3 h. And the concentration of 7-HCG in the target organ kidney was about 4 times higher than that in blood. SIGNIFICANCE Our findings indicate that 7-HCG could exert its protective effect against cisplatin-induced acute kidney injury by inhibiting apoptosis via p38 MAPK regulation and elucidates its pharmacokinetics.
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Affiliation(s)
- Haijie Wu
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, PR China
| | - Xiaohu Shi
- Department of Traditional Chinese Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, PR China
| | - Yingda Zang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, PR China
| | - Xiaodi Zhao
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, PR China
| | - Xikun Liu
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, PR China
| | - Weida Wang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, PR China
| | - Wenying Shi
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, PR China
| | - Clarence T T Wong
- Department of Applied Biology and Chemical Technology and State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Li Sheng
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, PR China.
| | - Xiaoguang Chen
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, PR China.
| | - Sen Zhang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, PR China.
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5
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Xiong J, Cheung YK, Fong WP, Wong CTT, Ng DKP. Selective photodynamic eradication of senescent cells with a β-galactosidase-activated photosensitiser. Chem Commun (Camb) 2023; 59:3471-3474. [PMID: 36877479 DOI: 10.1039/d2cc06661k] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
A β-galactosidase-responsive photosensitiser has been designed and synthesised. It contains a galactosyl substrate, a boron dipyrromethene-based photosensitising unit and a black hole quencher 2 connected via an AB2-type self-immolative linker. This novel photosensitiser can be selectively activated by the senescence-associated β-galactosidase in senescent cells, leading to restoration in fluorescence emission and effective killing of the cells via photodynamic action.
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Affiliation(s)
- Junlong Xiong
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
| | - Ying-Kit Cheung
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Wing-Ping Fong
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Clarence T T Wong
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Dennis K P Ng
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
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6
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Chu JCH, Wong CTT, Ng DKP. Toward Precise Antitumoral Photodynamic Therapy Using a Dual Receptor-Mediated Bioorthogonal Activation Approach. Angew Chem Int Ed Engl 2023; 62:e202214473. [PMID: 36376249 DOI: 10.1002/anie.202214473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Indexed: 11/16/2022]
Abstract
Targeted delivery and specific activation of photosensitizers can greatly improve the treatment outcome of photodynamic therapy. To this end, we report herein a novel dual receptor-mediated bioorthogonal activation approach to enhance the tumor specificity of the photodynamic action. It involves the targeted delivery of a biotinylated boron dipyrromethene (BODIPY)-based photosensitizer, which is quenched in the native form by the attached 1,2,4,5-tetrazine unit, and an epidermal growth factor receptor (EGFR)-targeting cyclic peptide conjugated with a bicycle[6.1.0]non-4-yne moiety. Only for cancer cells that overexpress both the biotin receptor and EGFR, the two components can be internalized preferentially where they undergo an inverse electron-demand Diels-Alder reaction, leading to restoration of the photodynamic activity of the BODIPY core. By using a range of cell lines with different expression levels of these two receptors, we have demonstrated that this stepwise "deliver-and-click" approach can confine the photodynamic action on a specific type of cancer cells.
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Affiliation(s)
- Jacky C H Chu
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Clarence T T Wong
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.,Current address: Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China
| | - Dennis K P Ng
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
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7
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Chu JCH, Wong CTT, Ng DKP. Toward Precise Antitumoral Photodynamic Therapy Using a Dual Receptor‐Mediated Bioorthogonal Activation Approach. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202214473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
| | - Clarence T. T. Wong
- The Hong Kong Polytechnic University Applied Biology and Chemical Technology CHINA
| | - Dennis K. P. Ng
- The Chinese University of Hong Kong Chemistry Shatin, N.T. Hong Kong Hong Kong CHINA
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8
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Xiong J, Chu JCH, Fong WP, Wong CTT, Ng DKP. Specific Activation of Photosensitizer with Extrinsic Enzyme for Precisive Photodynamic Therapy. J Am Chem Soc 2022; 144:10647-10658. [PMID: 35639988 DOI: 10.1021/jacs.2c04017] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Delivery of functional proteins into the intracellular space has been a challenging task that could lead to a myriad of therapeutic applications. We report herein a novel bioconjugation strategy for enzyme modification and selective delivery into cancer cells for lock-and-key-type activation of photosensitizers. Using a bifunctional linker containing a bis(bromomethyl)phenyl group and an o-phthalaldehyde moiety, it could induce cyclization of the peptide sequence Ac-NH-CRGDfC-CONH2 through site-specific dibenzylation with the two cysteine residues and further coupling with β-galactosidase via the phthalaldehyde-amine capture reaction. This facile two-step one-pot procedure enabled the preparation of cyclic RGD-modified β-galactosidase readily, which could be internalized selectively into αvβ3 integrin-overexpressed cancer cells. Upon encountering an intrinsically quenched distyryl boron dipyrromethene-based photosensitizer conjugated with a galactose moiety through a self-immolative linker inside the cells, the extrinsic enzyme induced specific cleavage of the β-galactosidic bond followed by self-immolation to release an activated derivative, thereby restoring the photodynamic activities and causing cell death effectively. The high specificity of this extrinsic enzyme-activated photosensitizing system was also demonstrated in vivo using nude mice bearing an αvβ3 integrin-positive U87-MG tumor. The specific activation at the tumor site resulted in lighting up and complete eradication of the tumor upon laser irradiation, while by using the native β-galactosidase, the effects were largely reduced. In contrast to the conventional activation using intrinsic enzymes, this extrinsic enzyme activatable approach can further minimize the nonspecific activation toward precisive photodynamic therapy.
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Affiliation(s)
- Junlong Xiong
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Jacky C H Chu
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Wing-Ping Fong
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Clarence T T Wong
- Department of Applied Biology and Chemical Technology and State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Dennis K P Ng
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
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9
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Chu JCH, Shao C, Ha SYY, Fong WP, Wong CTT, Ng DKP. One-pot peptide cyclisation and surface modification of photosensitiser-loaded red blood cells for targeted photodynamic therapy. Biomater Sci 2021; 9:7832-7837. [PMID: 34726672 DOI: 10.1039/d1bm01306h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report herein a one-pot approach to cyclise a tumour-targeting peptide and conjugate it on the surface of red blood cells loaded with a boron dipyrromethene-based photosensitiser using a bifunctional linker consisting of a bis(bromomethyl)phenyl unit and an ortho-phthalaldehyde unit. This cell-based photosensitiser with surface modification with cyclic RGD peptide moieties can selectively bind against the αvβ3 integrin-overexpressed cancer cells, leading to enhanced photocytotoxicity. The results demonstrate that this facile strategy is effective for live-cell surface modification for a wide range of applications.
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Affiliation(s)
- Jacky C H Chu
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
| | - Chihao Shao
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China.
| | - Summer Y Y Ha
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
| | - Wing-Ping Fong
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Clarence T T Wong
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China.
| | - Dennis K P Ng
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
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10
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Chu JCH, Fong WP, Wong CTT, Ng DKP. Facile Synthesis of Cyclic Peptide-Phthalocyanine Conjugates for Epidermal Growth Factor Receptor-Targeted Photodynamic Therapy. J Med Chem 2021; 64:2064-2076. [PMID: 33577327 DOI: 10.1021/acs.jmedchem.0c01677] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A facile procedure for in situ peptide cyclization and phthalocyanine conjugation was developed by utilizing a bifunctional linker incorporated with a bis(bromomethyl)benzene unit and a cyclopentadiene moiety. These functional groups facilitated the nucleophilic substitution with the two cysteine residues of the linear peptides followed by the Diels-Alder reaction with the maleimide moiety attached to a zinc(II) phthalocyanine. With this approach, three cyclic peptide-phthalocyanine conjugates were prepared in 20-26% isolated yield via a one-pot procedure. One of the conjugates containing a cyclic form of the epidermal growth factor receptor (EGFR)-binding peptide sequence CMYIEALDKYAC displayed superior features as an advanced photosensitizer. It showed preferential uptake by two EGFR-positive cancer cell lines (HT29 and HCT116) compared with two EGFR-negative counterparts (HeLa and HEK293), resulting in significantly higher photocytotoxicity. Intravenous administration of this conjugate into HT29 tumor-bearing nude mice resulted in selective localization in tumor and effective inhibition of tumor growth upon photodynamic treatment.
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Affiliation(s)
- Jacky C H Chu
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Wing-Ping Fong
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Clarence T T Wong
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Dennis K P Ng
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
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11
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Chu JCH, Chin ML, Wong CTT, Hui M, Lo P, Ng DKP. One‐Pot Synthesis of a Cyclic Antimicrobial Peptide‐Conjugated Phthalocyanine for Synergistic Chemo‐Photodynamic Killing of Multidrug‐Resistant Bacteria. Adv Therap 2020. [DOI: 10.1002/adtp.202000204] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Jacky C. H. Chu
- Department of Chemistry The Chinese University of Hong Kong, Shatin, New Territories Hong Kong China
| | - Miu Ling Chin
- Department of Microbiology The Chinese University of Hong Kong, Shatin, New Territories Hong Kong China
| | - Clarence T. T. Wong
- Department of Chemistry The Chinese University of Hong Kong, Shatin, New Territories Hong Kong China
| | - Mamie Hui
- Department of Microbiology The Chinese University of Hong Kong, Shatin, New Territories Hong Kong China
| | - Pui‐Chi Lo
- Department of Biomedical Sciences City University of Hong Kong Tat Chee Avenue, Kowloon Hong Kong China
| | - Dennis K. P. Ng
- Department of Chemistry The Chinese University of Hong Kong, Shatin, New Territories Hong Kong China
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12
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Chu JCH, Yang C, Fong WP, Wong CTT, Ng DKP. Facile one-pot synthesis of cyclic peptide-conjugated photosensitisers for targeted photodynamic therapy. Chem Commun (Camb) 2020; 56:11941-11944. [PMID: 32931540 DOI: 10.1039/d0cc05264g] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A novel synthetic strategy for in situ cyclisation of peptides and conjugation with functional boron dipyrromethenes (BODIPYs) has been developed. Linear peptides with up to 16 amino acid residues can be cyclised effectively and the resulting conjugates can be isolated in higher than 20% yield. One of the conjugates having a cyclic RGD moiety has been studied both in vitro and in vivo. It exhibits high and selective affinity towards the αvβ3-positive cell lines and induces high photocytotoxicity. The conjugate can also selectively localise in and effectively inhibit the growth of αvβ3-overexpressed tumour in vivo.
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Affiliation(s)
- Jacky C H Chu
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
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13
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Wong CTT, Chu JCH, Ha SYY, Wong RCH, Dai G, Kwong TT, Wong CH, Ng DKP. Phthalaldehyde-Amine Capture Reactions for Bioconjugation and Immobilization of Phthalocyanines. Org Lett 2020; 22:7098-7102. [PMID: 32806143 DOI: 10.1021/acs.orglett.0c02398] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A phthalaldehyde-substituted phthalocyanine has been synthesized that can conjugate with a range of biomolecules, including peptides, monosaccharides, lipids, and DNAs, and be immobilized on the surface of bovine serum album nanoparticles and glass slides using the versatile and efficient phthalaldehyde-amine capture reactions. The light-induced cytotoxic effects of the latter two materials have also been examined against cancer cells and bacteria, respectively, showing that they are highly efficient photosensitizing systems for photodynamic therapy.
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Affiliation(s)
- Clarence T T Wong
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Jacky C H Chu
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Summer Y Y Ha
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Roy C H Wong
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Gaole Dai
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Tsz-Tung Kwong
- Department of Clinical Oncology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Chi-Hang Wong
- Department of Clinical Oncology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Dennis K P Ng
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
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14
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Abstract
Cyclic peptides are drawing wide attention as potential medium-sized modulators of biomolecular interactions with large binding surfaces. Simple but effective peptide cyclization methods are needed to construct cyclic peptide libraries by both peptide and nonpeptide chemists. Herein, we report a highly chemoselective and operation-simple method directly cyclizing unprotected peptides, in which ortho-phthalaldehyde (OPA) is found to react with the lysine/N-terminus and cysteine within one unprotected peptide sequence effectively to form the isoindole-bridged cyclic peptides. This reaction is carried out in the aqueous buffer and features tolerance of diverse functionalities, rapid and clean transformation, and operational simplicity. In addition, OPA peptide cyclization can also be combined with native chemical ligation-mediated cyclization to generate bicyclic peptides. Furthermore, the OPA peptide cyclization product can further react with the N-maleimide moiety in a one-pot manner to introduce additional functional motifs, like a fluorophore probe, biomolecules (e.g., glycan, peptide, or DNA). This OPA-cyclization method extends the toolbox for integrating postcyclization modification and bioconjugation into peptide cyclization with an all-in-one manner strategy.
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Affiliation(s)
- Yue Zhang
- Department of Chemistry, State Key Laboratory of Synthetic Chemistry , The University of Hong Kong , Hong Kong , P. R. China , SAR
| | - Qing Zhang
- Department of Chemistry, State Key Laboratory of Synthetic Chemistry , The University of Hong Kong , Hong Kong , P. R. China , SAR
| | - Clarence T T Wong
- Department of Chemistry , The Chinese University of Hong Kong , Hong Kong , P. R. China , SAR
| | - Xuechen Li
- Department of Chemistry, State Key Laboratory of Synthetic Chemistry , The University of Hong Kong , Hong Kong , P. R. China , SAR
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15
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Xue EY, Wong RCH, Wong CTT, Fong WP, Ng DKP. Synthesis and biological evaluation of an epidermal growth factor receptor-targeted peptide-conjugated phthalocyanine-based photosensitiser. RSC Adv 2019; 9:20652-20662. [PMID: 35515550 PMCID: PMC9065697 DOI: 10.1039/c9ra03911b] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 06/21/2019] [Indexed: 12/15/2022] Open
Abstract
A peptide-conjugated zinc(ii) phthalocyanine containing the epidermal growth factor receptor-targeted heptapeptide QRHKPRE has been prepared. The conjugate labelled as ZnPc-QRH* can selectively bind to the cell membrane of HT29 human colorectal adenocarcinoma cells in 10 min followed by internalisation upon prolonged incubation via receptor-mediated endocytosis, leading to localisation in lysosomes eventually. By manipulating the incubation time, the subcellular localisation of the conjugate can be varied and the cell-death pathways induced upon irradiation can also be altered. It has been found that photosensitisation initiated at the cell membrane and in the lysosomes would trigger cell death mainly through necrosis and apoptosis respectively. Intravenous administration of the conjugate into HT29 tumour-bearing nude mice resulted in higher accumulation in the tumour than in most major organs. The selective binding of this conjugate to tumour has also been demonstrated by comparing the results with those of the analogue with a scrambled peptide sequence (EPRQRHK). The overall results indicate that ZnPc-QRH* is a promising EGFR-targeted photosensitiser for photodynamic therapy.
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Affiliation(s)
- Evelyn Y Xue
- Department of Chemistry, The Chinese University of Hong Kong Shatin, N.T. Hong Kong China
| | - Roy C H Wong
- Department of Chemistry, The Chinese University of Hong Kong Shatin, N.T. Hong Kong China
| | - Clarence T T Wong
- Department of Chemistry, The Chinese University of Hong Kong Shatin, N.T. Hong Kong China
| | - Wing-Ping Fong
- School of Life Sciences, The Chinese University of Hong Kong Shatin, N.T. Hong Kong China
| | - Dennis K P Ng
- Department of Chemistry, The Chinese University of Hong Kong Shatin, N.T. Hong Kong China
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16
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Lee CL, Liu H, Wong CTT, Chow HY, Li X. Enabling N-to-C Ser/Thr Ligation for Convergent Protein Synthesis via Combining Chemical Ligation Approaches. J Am Chem Soc 2016; 138:10477-84. [DOI: 10.1021/jacs.6b04238] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Chi Lung Lee
- Department of Chemistry,
The State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Han Liu
- Department of Chemistry,
The State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Clarence T. T. Wong
- Department of Chemistry,
The State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Hoi Yee Chow
- Department of Chemistry,
The State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Xuechen Li
- Department of Chemistry,
The State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
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17
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Abstract
ortho-Phthalaldehyde (OPA) and its derivatives are found to react chemoselectively with amino groups on peptides and proteins rapidly and tracelessly under the physiological condition via formation of phthalimidines, which provides a novel and promising approach when performing bioconjugation on native proteins. The notable advantages of this method over the existing native protein lysine-labeling approaches include a traceless process, a self-reacting, specific and fast reaction, ease of operation, and the ability to use nonhydrolyzable reagents. Its applications have been effectively demonstrated including conjugation of peptides and proteins, and generation of an active PEGlyated l-asparaginase.
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Affiliation(s)
- Chun Ling Tung
- Department of Chemistry, The State Key Laboratory of Synthetic Chemistry, The University of Hong Kong , Hong Kong, China
| | - Clarence T T Wong
- Department of Chemistry, The State Key Laboratory of Synthetic Chemistry, The University of Hong Kong , Hong Kong, China
| | - Eva Yi Man Fung
- Department of Chemistry, The State Key Laboratory of Synthetic Chemistry, The University of Hong Kong , Hong Kong, China
| | - Xuechen Li
- Department of Chemistry, The State Key Laboratory of Synthetic Chemistry, The University of Hong Kong , Hong Kong, China
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18
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Tung CL, Wong CTT, Li X. Peptide 2-formylthiophenol esters do not proceed through a Ser/Thr ligation pathway, but participate in a peptide aminolysis to enable peptide condensation and cyclization. Org Biomol Chem 2015; 13:6922-6. [DOI: 10.1039/c5ob00825e] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Peptide thiol salicylaldehyde esters unexpectedly do not follow a Ser/Thr ligation pathway, but proceed towards a peptide aminolysis in DMSO.
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Affiliation(s)
- Chun Ling Tung
- Department of Chemistry
- State Key Laboratory of Synthetic Chemistry
- The University of Hong Kong
- China
- Chong Yuet Ming Chemistry Building
| | - Clarence T. T. Wong
- Department of Chemistry
- State Key Laboratory of Synthetic Chemistry
- The University of Hong Kong
- China
- Chong Yuet Ming Chemistry Building
| | - Xuechen Li
- Department of Chemistry
- State Key Laboratory of Synthetic Chemistry
- The University of Hong Kong
- China
- Chong Yuet Ming Chemistry Building
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19
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Wong CTT, Li T, Lam HY, Zhang Y, Li X. Realizing serine/threonine ligation: scope and limitations and mechanistic implication thereof. Front Chem 2014; 2:28. [PMID: 24904921 PMCID: PMC4033038 DOI: 10.3389/fchem.2014.00028] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 04/29/2014] [Indexed: 11/13/2022] Open
Abstract
Serine/Threonine ligation (STL) has emerged as an alternative tool for protein chemical synthesis, bioconjugations as well as macrocyclization of peptides of various sizes. Owning to the high abundance of Ser/Thr residues in natural peptides and proteins, STL is expected to find a wide range of applications in chemical biology research. Herein, we have fully investigated the compatibility of the STL strategy for X-Ser/Thr ligation sites, where X is any of the 20 naturally occurring amino acids. Our studies have shown that 17 amino acids are suitable for ligation, while Asp, Glu, and Lys are not compatible. Among the working 17 C-terminal amino acids, the retarded reaction resulted from the bulky β-branched amino acid (Thr, Val, and Ile) is not seen under the current ligation condition. We have also investigated the chemoselectivity involving the amino group of the internal lysine which may compete with the N-terminal Ser/Thr for reaction with the C-terminal salicylaldehyde (SAL) ester aldehyde group. The result suggested that the free internal amino group does not adversely slow down the ligation rate.
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Affiliation(s)
- Clarence T T Wong
- Department of Chemistry, The University of Hong Kong Hong Kong, China ; State Key Laboratory of Synthetic Chemistry, University of Hong Kong Hong Kong, China
| | - Tianlu Li
- Department of Chemistry, The University of Hong Kong Hong Kong, China ; State Key Laboratory of Synthetic Chemistry, University of Hong Kong Hong Kong, China
| | - Hiu Yung Lam
- Department of Chemistry, The University of Hong Kong Hong Kong, China ; State Key Laboratory of Synthetic Chemistry, University of Hong Kong Hong Kong, China
| | - Yinfeng Zhang
- Department of Chemistry, The University of Hong Kong Hong Kong, China ; State Key Laboratory of Synthetic Chemistry, University of Hong Kong Hong Kong, China
| | - Xuechen Li
- Department of Chemistry, The University of Hong Kong Hong Kong, China ; State Key Laboratory of Synthetic Chemistry, University of Hong Kong Hong Kong, China ; Shenzhen Institute of Research and Innovation of The University of Hong Kong Shenzhen, China
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20
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Wong CTT, Lam HY, Song T, Chen G, Li X. Synthesis of Constrained Head-to-Tail Cyclic Tetrapeptides by an Imine-Induced Ring-Closing/Contraction Strategy. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201304773] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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21
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Wong CTT, Lam HY, Song T, Chen G, Li X. Synthesis of constrained head-to-tail cyclic tetrapeptides by an imine-induced ring-closing/contraction strategy. Angew Chem Int Ed Engl 2013; 52:10212-5. [PMID: 23934633 DOI: 10.1002/anie.201304773] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Indexed: 02/03/2023]
Affiliation(s)
- Clarence T T Wong
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong (P.R. China)
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22
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Lam HY, Zhang Y, Liu H, Xu J, Wong CTT, Xu C, Li X. Total Synthesis of Daptomycin by Cyclization via a Chemoselective Serine Ligation. J Am Chem Soc 2013; 135:6272-9. [DOI: 10.1021/ja4012468] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Hiu Yung Lam
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s
Republic of China
| | - Yinfeng Zhang
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s
Republic of China
| | - Han Liu
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s
Republic of China
| | - Jianchao Xu
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s
Republic of China
| | - Clarence T. T. Wong
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s
Republic of China
| | - Ci Xu
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s
Republic of China
| | - Xuechen Li
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s
Republic of China
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23
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Wong CTT, Lam HY, Li X. Effective synthesis of kynurenine-containing peptides via on-resin ozonolysis of tryptophan residues: synthesis of cyclomontanin B. Org Biomol Chem 2013; 11:7616-20. [DOI: 10.1039/c3ob41631c] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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Abstract
Circular proteins, once thought to be rare, are now commonly found in plants. Their chemical synthesis, once thought to be difficult, is now readily achievable. The enabling methodology is largely due to the advances in entropic chemical ligation to overcome the entropy barrier in coupling the N- and C-terminal ends of large peptide segments for either intermolecular ligation or intramolecular ligation in end-to-end cyclization. Key elements of an entropic chemical ligation consist of a chemoselective capture step merging the N and C termini as a covalently linked O/S-ester intermediate to permit the subsequent step of an intramolecular O/S-N acyl shift to form an amide. Many ligation methods exploit the supernucleophilicity of a thiol side chain at the N terminus for the capture reaction, which makes cysteine-rich peptides ideal candidates for the entropy-driven macrocyclization. Advances in desulfurization and modification of the thiol-containing amino acids at the ligation sites to other amino acids add extra dimensions to the entropy-driven ligation methods. This minireview describes recent advances of entropy-driven ligation to prepare circular proteins with or without a cysteinyl side chain.
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Affiliation(s)
- James P Tam
- School of Biological Sciences, Nanyang Technological University, Singapore 637551.
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Wong CTT, Rowlands DK, Wong CH, Lo TWC, Nguyen GKT, Li HY, Tam JP. Orally Active Peptidic Bradykinin B1 Receptor Antagonists Engineered from a Cyclotide Scaffold for Inflammatory Pain Treatment. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201200984] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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27
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Wong CTT, Rowlands DK, Wong CH, Lo TWC, Nguyen GKT, Li HY, Tam JP. Orally Active Peptidic Bradykinin B1 Receptor Antagonists Engineered from a Cyclotide Scaffold for Inflammatory Pain Treatment. Angew Chem Int Ed Engl 2012; 51:5620-4. [DOI: 10.1002/anie.201200984] [Citation(s) in RCA: 183] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Indexed: 01/06/2023]
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28
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Wong CTT, Taichi M, Nishio H, Nishiuchi Y, Tam JP. Optimal Oxidative Folding of the Novel Antimicrobial Cyclotide from Hedyotis biflora Requires High Alcohol Concentrations. Biochemistry 2011; 50:7275-83. [DOI: 10.1021/bi2007004] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Clarence T. T. Wong
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive,
Singapore 637551
| | - Misako Taichi
- SAITO
Research Center, Peptide Institute, Inc., 7-2-9 Saito-Asagi, Ibaraki-shi,
Osaka 567-0085, Japan
| | - Hideki Nishio
- SAITO
Research Center, Peptide Institute, Inc., 7-2-9 Saito-Asagi, Ibaraki-shi,
Osaka 567-0085, Japan
| | - Yuji Nishiuchi
- SAITO
Research Center, Peptide Institute, Inc., 7-2-9 Saito-Asagi, Ibaraki-shi,
Osaka 567-0085, Japan
| | - James P. Tam
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive,
Singapore 637551
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