Lysine protection

BW Bycroft, WC Chan, SR Chhabra, ND Hone. A novel lysine-protecting procedure for continous flow solid phase synthesis of branched peptides. (Dde group) J Chem Soc Chem Commun 778, 1993. 

D-Ala-D-Ala) [32] followed by removal of the lysine-protecting group with three equivalents of LiOH in THF/water at pH 11 for 2 hr at room temperature, followed by neutralization to pH 7.0. This method ensured that pentapeptide was linked via the N-terminus, thus exposing the maximum amount of peptide for antibody recognition. The antibody produced by the rabbits was affinity purified using pentapeptide as a ligand, and then stored at 1 mg/ml in PBS with 10% glycerol and sodium azide at -20°C. 

The three orthogonally removable lysine protecting groups we use here are Fmoc (9-fluorenyl methoxy carbonyl), cleavable with 20% base, preferably with 20% piperidine or 3% DBU (l,8-diazabicyclo[5.4.0]undec-7-ene) (18), Dde (1-(4,4-dimethyl-2,6-dioxocyclohexylidene)-ethyl), cleavable with 2% hydrazine, and Aloe (allyloxy carbonyl), cleavable with palladium. Hydrazine also removes Fmoc, and thus it can be applied only if no Fmoc groups are present on the growing peptide chain. Acid-sensitive amino protecting groups available are Boc (tert-butyloxy carbonyl), cleavable with 90% TFA, and Mtt (4-methyl-trityl), cleavable with 1% TFA. We use Boc for the protection of the N-terminal moieties of N-terminal amino acids in each peptide chain as well as at the N-terminus of the scaffold. 

The following 12-residue peptides were synthesized in the same manner, starting with Boc-Val-PAM resin, but with the e-amino group of lysine protected with Fmoc (instead of Cl-Z) ... 

A branched peptide 11 [prothrombin(l-9)-Lys(Leu-enkephalin)-NH2] has been synthesized on a PAL-PEG-PSty resin in a continuous flow peptide synthesizert l by combining A -Fmoc for temporary protection, A -Aloc for semipermanent lysine protection, and Boc for permanent protection of the terminal amino group of prothrombin, as outlined in Scheme 6. Deprotection of Aloe in the continuous flow synthesizer is achieved by use of the Pd(PPh3)4/ NMM/ACOH/CHCI3 system. 

The use of PNZ derivatives in conjunction with Fmoc chemistry results in fewer problems with aspartamide and diketopiperazine formation and it is superior to the use of the Alloc group for ornithine and lysine protection in Fmoc based peptide synthesis."... 

Another biomedical appHcation of mictocapsules is the encapsulation of Hve mammalian ceUs for transplantation into humans. The purpose of encapsulation is to protect the transplanted ceUs or organisms from rejection by the host. The capsule sheU must prevent entrance of harmful agents into the capsule, aUow free transport of nutrients necessary for ceU functioning into the capsule, and aUow desirable ceUular products to freely escape from the capsule. This type of encapsulation has been carried out with a number of different types of Hve ceUs, but studies with encapsulated pancreatic islets or islets of Langerhans ate most common. The alginate—poly(L-lysine) encapsulation process originally developed in 1981 (54) catalyzed much of the ceU encapsulation work carried out since. A discussion of the obstacles to the appHcation of microencapsulation in islet transplantation reviewed much of the mote recent work done in this area (55). Animal ceU encapsulation has also been researched (56). 

In Industrial Chemicals. Recendy, as some amino acids (eg, L-glutamic acid, L-lysine, glycine, DL-alanine, DL-methionine) have become less expensive chemical materials, they have been employed in various appHcation fields. Poly(amino acid)s are attracting attention as biodegradable polymers in connection with environmental protection (236). 

A copper chelate selectively protects the q -NH2 group in lysine. The chelate is cleaved by 2 A HCl or by EDTA (H02CCH2)2NCH2CH2N(CH2C02H)2. ... 

Benzylsulfonamides, prepared in 40-70% yield, are cleaved by reduction (Na, NH3, 75% yield H2, Raney Ni, 65-85% yield, but not by H2, Pt02) and by acid hydrolysis (HBr or HI, slow). They are also cleaved by photolysis (2-4 h, 40-90% yield). The similar p-methylbenzylsulfonamide (PMS—NR2) has been prepared to protect the e-amino group in lysine it is quantitatively cleaved by anhydrous hydrogen fluoride/anisole (—20°, 60 min). Another example of this seldom used group is illustrated below... 

A CONVENIENT PREPARATION OF AN ORTHOGONALLY PROTECTED C ,C -DISUBSTITUTED AMINO ACID ANALOG OF LYSINE l-tert-BUTYLOXYCARBONYL-4-((9-FLUORENYLMETHYLOXYCARBONYL)AMINO)-PIPERIDINE-4-... 

The Jing group investigated their poly(L-lysine)-6-poly(L-phenylalanine) vesicles for the development of synthetic blood, since PEG-lipid vesicles were previously used to encapsulate hemoglobin to protect it from oxidation and to increase circulation time. They extended this concept and demonstrated that functional hemoglobin could be encapsulated into their vesicles. The same polypeptide material was also used to complex DNA, which caused the vesicles to lose their... 

In this work we will focus on the use of the cubic phase as a delivery system for oligopeptides - Desmopressin, Lysine Vasopressin, Somatostatin and the Renin inhibitor H214/03. The amino acid sequences of these peptides are given in Table I. The work focuses on the cubic phase as a subcutaneous or intramuscular depot for extended release of peptide drugs, and as a vehicle for peptide uptake in the Gl-tract. Several examples of how the peptide drugs interact with this lipid-water system will be given in terms of phase behaviour, peptide self-diffusion, in vitro and in vivo release kinetics, and the ability of the cubic phase to protect peptides from enzymatic degradation in vitro. Part of this work has been described elsewhere (4-6). 

The lysine binding sites on free Lys-plasminogen or free Lys-plasmin are susceptible to inhibition by a2 plasmin, the primary inhibitor of plasmin, because these sites are not protected by interaction with fibrin. However, when Lys-plasminogen is tightly bound to the fragment E domain, it is rapidly activated by the... 

Transition-metal phosphorus trichalcogenides such as MnPS3 are able to intercalate amino acids and peptides by ion exchange. In this way, increases in the basal spacing of 0.7 and 3-4 nm are observed for the intercalation of poly-L-lysine and lysozyme, respectively [224]. Interestingly, the enzymatic activity of the immobilized protein has been detected, suggesting that the enzyme is protected against denaturation. 

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