title: Design, synthesis, characterization and in-vivo activity of a novel salmon calcitonin conjugate containing a novel PEG-lipid moiety.
abstract: OBJECTIVE
  The aim of the study was to explore (1) the synthesis of a novel poly(ethylene glycol) modified lipid (PEG-lipid, PL) containing a chemically active tri-block linker, epsilon-maleimido lysine (Mal), and its conjugation with salmon calcitonin (sCT), and (2) the biophysical properties and activity of the resulting conjugate, Mal-PL-sCT, relative to the control, 2PEG-Mal-sCT, which comprises sCT conjugated with alpha-palmitoyl-N-epsilon-maleimido-L-lysine at cysteine 1 and cysteine 7, and PEG moieties at lysine 11 and lysine 18 via a conventional stepwise method.
  
  
  METHODS
  The PEG-lipid was obtained by condensing palmitic acid derivative of epsilon-maleimido lysine with methoxy poly(ethylene glycol) amine. Under reductive conditions, the PEG-lipid readily reacted with sCT to yield the resultant compound, Mal-PL-sCT.
  
  
  RESULTS
  Dynamic light scattering analyses suggested that Mal-PL-sCT and 2PEG-Mal-sCT exhibited robust helical structures with a high tendency to aggregate in water. Both compounds were more stable against intestinal degradation than sCT, although Mal-PL-sCT was less stable than 2PEG-Mal-sCT. However, 2PEG-Mal-sCT did not possess hypocalcaemic activity while Mal-PL-sCT retained the hypocalcaemic activity of sCT when it was subcutaneously injected in the rat model. Multiple functional groups may be conjugated to a peptide via a tri-block linker without the risk of obliterating the intrinsic bioactivity of the peptide.
  
  
  CONCLUSIONS
  The resultant novel PEG-lipid has a potential role to optimize protein and peptide delivery.
authors.affiliation: Department of Pharmacy, National University of Singapore, Singapore.
authors.forename: Weiqiang
authors.initials: W
authors.lastname: Cheng
authors.forename: Lee-Yong
authors.initials: LY
authors.lastname: Lim
mesh_terms: D000818:Animals; D002116:Calcitonin / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D002118:Calcium / Q000097:blood; D002942:Circular Dichroism; D004063:Digestion; D004337:Drug Carriers / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D015195:Drug Design; D005260:Female; D005782:Gels / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D008239:Lysine / Q000031:analogs & derivatives / Q000737:chemistry; D009391:Nephelometry and Turbidimetry; D010024:Osteoporosis / Q000097:blood / Q000188:drug therapy; D010316:Particle Size; D011092:Polyethylene Glycols / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D017433:Protein Structure, Secondary; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013997:Time Factors
chemical_list: C551988:2PEG-Mal-sCT; D004337:Drug Carriers; D005782:Gels; C551989:Mal-PL-sCT; C401288:methoxy polyethylene glycol amine; D011092:Polyethylene Glycols; C028815:salmon calcitonin; D002116:Calcitonin; D008239:Lysine; D002118:Calcium