Synthesis of New Peptide Derivatives of Galanthamine Designed for Prevention and Treatment of Alzheimer's Disease.

New derivatives of galanthamine containing peptide fragments with ß-secretase inhibitor activity were synthesized. In position 6 of the galanthamine new shortened analogues of ß-secretase inhibitor OM 99-2 (Boc-Val-Asn-Leu-Ala-OH and Boc-Val-Asn-Leu-Ala-Val-OH) were included. The new derivatives of the galanthamine in position 11 including Boc and norgalanthamine in P3 or P4 positions, Val in P2' position and benzylamin in P3'-position were also synthesized. All new peptides were investigated on mice for acute toxicity. The test compounds were administered to mice via intraperitoneal (i.p.) route. They have low toxicity (LD50>1000 mg/kg) after i.p. The compound 11-N-demethyl-11-N-N-[Boc-Asp(Asp-Leu-Ala-Val-NH-Bzl)]-Galanthamine was investigated by two way active avoidance method. The compound has good influence on the conditioned reflexes, which improved the processes of learning and memory. Inhibition activity of newly synthesized compounds was monitored against BuChE and IC50 values are determined. All compounds show activity in micromolar concentration. Compounds 5 and 6 have around 10 times higher activity than galanthamine. Compounds 4 and 9 also show good activity. All newly synthesized compounds show low acute toxicity.

Equilibrium unfolding of dimeric human prostatic acid phosphatase involves an inactive monomeric intermediate.

Guanidine hydrochloride (GdnHCl)-induced unfolding of human prostatic acid phosphatase (hPAP), a homodimer of 50 kDa subunit molecular weight, was investigated with activity measurements, size exclusion HPLC, tryptophan fluorescence, 1-anilinonaphtalene-8-sulfonate (ANS) binding and reactivity with 2-(4'-maleimidoanilino)naphthalene-6-sulfonate (MIANS). Equilibrium analysis was performed to shed light on the role of dimerization in the folding and stability of the catalytically active oligomeric protein. Unfolding was reversible, as verified by activity measurements and tryptophan fluorescence. The noncoincidence of the unfolding curves obtained by different techniques suggests the occurrence of a multiphasic process. The reaction of hPAP inactivation is accompanied by dissociation of the dimer into two monomers. The midpoint of this transition is at 0.65 M GdnHCl with 4.24+/-0.12 kcalmol(-1) free energy change. Binding of ANS to the inactive phosphatase monomer, especially remarkable in the region from 0.8 to 1.25M GdnHCl, suggests that the hydrophobic probe indicates exposition of the intersubunit hydrophobic surface and a loosening of the monomer's tertiary structure. Strong fluorescence of thiol group derivatives, the products of their reaction with MIANS, appears in a limited range of GdnHCl concentrations (1.2-1.6M). This shows that in the relaxed structure of the intermediate, the reagent is allowed to penetrate into the hydrophobic environment of the partially hidden thiol groups. The equilibrium unfolding reaction of hPAP, as monitored by tryptophan fluorescence, does not depend on the protein concentration and displays a single transition curve with a midpoint at 1.7 M GdnHCl and value of DeltaG(unf)(H(2)O)=3.38+/-0.08 kcalmol(-1) per monomer, a result implying that this transition is related to the conformational change of the earlier dissociated and already inactive subunit of the protein.