9-Acridinylpeptides and 9-acridinyl-4-nitrophenylsulfonylpeptides

Discovery of metabolically stabilized electronegative polyacridine-PEG peptide DNA open polyplexes

Cationic condensing peptides and polymers bind electrostatically to DNA to form cationic polyplexes. While many cationic polyplexes are able to achieve in vitro transfection mediated through electrostatic interactions, few have been able to mediate gene transfer in vivo. The present study describes the development and testing of polyacridine PEG-peptides that bind to plasmid DNA by intercalation resulting in electronegative open polyplex DNA. Polyacridine PEG-peptides were prepared by chemically conjugating 6-(9-acridinylamino) hexanoic acid onto side chains of Lys in PEG-Cys-Trp-(Lys)(3, 4, or 5). The resulting PEG-Cys-Trp-(Lys-(Acr))(3, 4, or 5) peptides bound tightly to DNA by polyintercalation, rather than electrostatic binding. Unlike polycationic polyplexes, polyacridine PEG-peptide polyplexes were anionic and open coiled, as revealed by zeta potential and atomic force microscopy. PEG-Cys-Trp-(Lys-(Acr))(5) showed the highest DNA binding affinity and the greatest ability to protect DNA from metabolism by DNase. Polyacridine PEG-peptide DNA open polyplexes were dosed intramuscularly and electroporated in mice to demonstrate their functional activity in gene transfer. These results establish polyacridine PEG-peptide DNA open polyplexes as a novel gene delivery method for in vivo use.

New peptide conjugates with 9-aminoacridine: synthesis and binding to DNA

New peptides-9-aminoacridine conjugates with an ethylene diamine linker-have been synthesized (both solution and solid phase methods were used) and their interactions with DNA have been studied. The affinity of H-Phe-Gln-Gly-Ile(2)-NHCH(2)CH(2)NH-Acr conjugate and of its extended analogue containing 6-aminohexanoic acid to DNA were lower than that of a standard H-Gly-NHCH(2)CH(2)NH-Acr conjugate. The results fit well into our concept of peptide conjugates with lowered binding activity to DNA, which could be capable of unlimited extravascular distribution. Moreover, new structures could be potentially useful as the mild tuners of DNA interaction with strong bis-acridine binders.

Theoretical design of a bistetrapeptide derivative of mitoxantrone targeted towards the double-stranded hexanucleotide sequence d(GGCGCC)2

The hexanucleotide d(GGCGCC)2 is encountered in recurrent fashion within transcriptional activating sequences in retroviruses and protooncogenes. Our first theoretical design of novel oligopeptide derivatives of mitoxantrone, MTX (1), had enabled us to predict derivatives depsiGly-Lys(L) and depsiGly-Gly-Orn(D) to preferentially target the tetrameric core d(CCGG)2. Owing to the crucial importance of hexamer d(GGCGCC)2, we have attempted to extend the realm of our approach by now targeting this specific hexanucleotide. For that purpose, we undertook the design of further oligopeptide derivatives of MTX, in which each arm was identically amidated (rather than esterified as in (1)) by tri- or tetrapeptides of varying sequences and individual residue configurations. The binding affinities of these derivatives to the palindromic sequences d(GGCGCC)2, d(CGCGCG)2, d(GCCGGC)2 and d(CCCGGG)2, were compared by energy-minimization. We report here the results obtained with the most promising derivative, having the sequence Arg(L)-Gly-Val(L)-Glu(L), and displaying a considerable energy preference for d(GGCGCC)2 over the other candidate hexameric sites (referred to as I). In the corresponding complexes, the two arms are in two mutually antiparallel directions in the major groove, and adopt a beta-sheet like arrangement stabilized by two H-bonds involving the carbonyl and amide groups of the Gly residues. Each Arg side chain on a given arm chelates O6 and N7 atoms of G1, G2/G1', G2' with its imino and cis amino hydrogen, and is simultaneously bound through two amino hydrogens in a bidentate interaction with the Glu residue.

Theoretical design of novel, 4 base pair selective derivatives of mitoxantrone

Mitoxantrone (MTX) is a recently synthesized antitumor intercalative molecule, currently in use in chemotherapy. Previous theoretical computations showed that the base pair selectivity of MTX is limited to the sole two base-pair sequence making up the intercalation site. In order to further extend the recognition site, we undertook, by means of theoretical computations, the design of novel MTX derivatives, in which the terminal hydroxyl group of each side chain is esterified with oligopeptides. We compare in the present study the binding affinities of two derivatives, depsiGly-Lys(D) and depsiGly-Gly-Orn(L), for the palindromic sequences d(CCCGGG)2, d(GCCGGC)2, d(GGCGCC)2, and d(CGCGCG)2. Major groove binding of the oligopeptide arms was shown to be significantly more favourable than either minor groove binding, or binding to the sole phosphate groups. With the two arms adopting two antiparallel directions, two distinct arrangements were investigated in the major groove: (a) the two oligopeptides are brought closer together by means of two hydrogen bonds involving the backbone of their second residue in a beta-sheet like arrangement; (b) the two arms are remote from each other so as to reduce their mutual electrostatic repulsion. Whatever the disposition, the optimal binding configurations were invariably found to be those in which the cationic side chains of the terminal residues chelate N7/O6 of two successive guanines, whenever present on a given strand. A distinct energetical preference for arrangement (a) was obtained with the depsiGly-Gly-Orn(L) derivative. Replacement of the central Gly residue by a Cys one, as in the sequence depsiGly-Cys-Orn(L), was proposed subsequently, so as to further stabilize such a beta-sheet arrangement by means of a disulfide bridge between the two Cys residues. The two investigated compounds were shown to preferentially bind sequences d(CCCGGG)2 and d(GCCGGC)2, with a tetrameric core CCGG rather than sequences d(GGCGCC)2 and d(CGCGCG)2, with a tetrameric core GCGC.

Solid phase peptide synthesis utilizing 9-fluorenylmethoxycarbonyl amino acids

9-Fluorenylmethoxycarbonyl (Fmoc) amino acids were first used for solid phase peptide synthesis a little more than a decade ago. Since that time, Fmoc solid phase peptide synthesis methodology has been greatly enhanced by the introduction of a variety of solid supports, linkages, and side chain protecting groups, as well as by increased understanding of solvation conditions. These advances have led to many impressive syntheses, such as those of biologically active and isotopically labeled peptides and small proteins. The great variety of conditions under which Fmoc solid phase peptide synthesis may be carried out represents a truly "orthogonal" scheme, and thus offers many unique opportunities for bioorganic chemistry.