Fmoc-Lys(Boc)-OH

Fmoc-Lys(Boc)-OH

Fluoreometric behavior of a novel bis-acridine orange bound to double stranded DNA.[Pubmed:14510425]

Nucleic Acids Res Suppl. 2003;(3):151-2.

Novel bis-acridine orange (1) was synthesized from Fmoc-Lys(Boc)-OH and Fmoc-Lys(AO)-OH (AO: acridine orange), with the 9-position of acridine orange (AO) linked to the epsilon-amino moiety of lysine, on the peptide synthesizer. Bis-acridine orange (1) yielded a very weak fluorescence in an aqueous media due to the intramolecular stacking, but its fluorescence was enhanced over 200-times upon binding to double-stranded DNA, irrespective of the DNA sequences. Circular dichroism (CD) spectra showed that 1 binds to double stranded DNA in its stacked conformation, concomitant with fluorescence enhancement.

Bis-naphthalene diimide exhibiting an effective bis-threading intercalating ability.[Pubmed:14510411]

Nucleic Acids Res Suppl. 2003;(3):123-4.

Bis-naphthalene diimide (1) was successfully synthesized from Fmoc-Lys(Boc)-OH and Fmoc-Lys(NDI)-OH on the automated peptide synthesizer. The absorption spectra of 1 suggested intramolecular stacking of the naphthalene diimide parts in buffer solution. Viscometric titration of a double stranded DNA (dsDNA) solution with 1 suggested that both of the naphthalene diimide parts of 1 are involved in threading intercalation. Kinetic studies suggested that 1 binds to dsDNA with a large affinity constant (K = 106 M(-1)) by "bis-threading intercalation" rather than by electrostatic binding between the cationic sites of lysine parts and phosphate anions of DNA.

Comparison of modification sites in glycated crystallin in vitro and in vivo.[Pubmed:25636230]

Anal Bioanal Chem. 2015 Mar;407(9):2557-67.

Glycation of alpha-crystallin is responsible for age- and diabetic-related cataracts, which are the main cause of blindness worldwide. We optimized the method of identification of lysine residues prone to glycation using the combination of LC-MS, isotopic labeling, and modified synthetic peptide standards with the glycated lysine derivative (Fmoc-Lys(i,i-Fru,Boc)-OH). The in vitro glycation of bovine lens alpha-crystallin was conducted by optimized method with the equimolar mixture of [(12)C6]- and [(13)C6]D-glucose. The in vivo glycation was studied on human lens crystallin. The glycated protein was subjected to proteolysis and analyzed using LC-MS. The results of in vitro and in vivo glycation of alpha-crystallin reveal a different distribution of the modified lysine residues. More Amadori products were detected as a result of the in vitro reaction due to forced glycation conditions. The developed method allowed us to identify the glycation sites in crystallin from eye lenses obtained from patients suffering from the cataract. We identified K166 in the A chain and K166 in the B chain of alpha-crystallin as major glycation sites during the in vitro reaction. We found also two in vivo glycated lysine residues: K92 in the B chain and K166 in the A chain, which are known as locations for Amadori products. These modification sites were confirmed by the LC-MS experiment using two synthetic standards. This study demonstrates the applicability of the LC-MS methods combined with the isotopic labeling and synthetic peptide standards for analysis of post-translational modifications in the biological material.

Pitfalls in the synthesis of fluorescent methotrexate oligopeptide conjugates.[Pubmed:27357306]

Amino Acids. 2016 Nov;48(11):2599-2604.

Methotrexate (MTX) conjugates with poly[Lys(DL-Alam)] based polymeric polypeptides are efficient against Leishmania donovani parasite infection, but the mechanism of the effect is not known yet. We prepared therefore the 5(6)-carboxyfluorescein (Cf) labeled oligopeptide [Cf-K(AaAa)] (a: D-alanine, A: L-alanine) and the corresponding MTX conjugates [Cf-K(MTX-AaAa)] as model compounds for structure-activity experiments. The conjugate aimed to be synthesized with solid phase methodology on MBHA resin with Boc strategy, using Fmoc-Lys(Boc)-OH. However, various side reactions were identified. Here we report three problems observed during the synthesis as well as solutions developed by us: (1) unexpected cyclopeptide-formation with the lactone-carboxylic group of the Cf was detected, when Cf was attached to the alpha-amino group of the Lys residue on solid phase. This was avoided by changing the order of Cf incorporation with using Fmoc/Dde strategy. Alternatively, we have built the peptide with Fmoc strategy on solid phase first and performed the labeling with Cf-OSu subsequently in solution. (2) During HF cleavage of the protected conjugates, MTX was demonstrated to form adducts with anisole and p-cresol scavengers, and the TMSOTf cleavage methodology was also found to be inadequate due to the large number of side products formed. We report here that using Fmoc/Dde strategy is an appropriate method to circumvent the cleavage with HF or TMSOTf. (3) During the coupling of MTX with oligopeptide, structural and stereo isomers are formed. We have described here the suitable conditions of HPLC separation of these products.

Trifluoroacetyl-HYNIC peptides: synthesis and 99mTc radiolabeling.[Pubmed:17315986]

J Med Chem. 2007 Mar 22;50(6):1418-22.

Fmoc-lys(HYNIC-Boc)-OH, a precursor for solid-phase synthesis of 99mTc-labeled peptides, was synthesized efficiently without HPLC purification. HPLC-ESMS showed that deprotection and decoupling of peptide from the resin with trifluoroacetic acid gave initially HYNIC-peptide, which was trifluoroacetylated upon prolonged incubation. The trifluoroacetyl-HYNIC group was hydrolyzed during 99mTc labeling, rendering deprotection unnecessary. Trifluoroacetyl-HYNIC peptide was 99mTc-labeled as efficiently, producing the same product, as HYNIC-peptide. These modifications enhance the versatility of HYNIC for 99mTc peptide labeling.