Opioid peptides: synthesis and biological properties of [(N gamma-glucosyl,N gamma-methoxy)-alpha, gamma-diamino-(S)-butanoyl]4-deltorphin-1-neoglycopeptide and related analogues

The [D-Ala2]deltorphin 1 sequence in which the aspartic acid residue is replaced by the N gamma-OCH3-alpha, gamma-diamino (S) butanoyl residue was synthesized using the Fmoc-chemistry-based solid phase procedure. The resulting deltorphin analogue was chemoselectively glucosylated by reaction with unprotected D-glucose (Glc). The Asn4-, (2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-galactopyranosyl)-Asn4- and the (2-acetamido-2-deoxy-D-galactopyranosyl)-Asn4-deltorphin I were also prepared for comparison. The affinity of the new compounds for the delta-opioid receptor was expressed by the inhibition constant (Ki) of the binding of the delta-receptor selective ligand [3H]naltrindole (NTI) to rat brain membrane preparations. The in vitro biological activity of the synthetic peptides was compared with that of the mu-opioid receptor agonist dermorphin in guinea pig ileum (GPI) preparations and with that of the delta-opioid receptor agonist deltorphin I in mouse vas deferens (MVD) preparations. The substitution of Asp4 with Asn failed to affect drastically the Ki and IC50 values for delta-sites, suggesting that an electrostatic interaction does not play an essential role in the binding to delta-opioid sites. The steric hindrance of the side chain of the residue in position 4 affects binding to delta-sites. The increase of the Ki value is smaller when the sugar-peptide linkage involves the gamma-nitrogen of the Dab residue in comparison with the Asn amide side chain.     

Demystifying the three dimensional structure of G protein-coupled receptors (GPCRs) with the aid of molecular modeling

We review our recent work on adenosine receptors, a family of GPCRs; focusing our attention on A3 adenosine receptor, we have demonstrated that the reciprocal integration of different theoretical and experimental disciplines can be very useful for the successful protein-based design of new, potent and selective receptor ligands.     

Numerical Approximation of Time Domain Electromagnetic Scattering from a Thin Wire

We present two new stable schemes for computing the current induced on the surface of a thin wire by an incident time-dependent electromagnetic field. The problem involves solving a retarded potential integral equation (RPIE). One algorithm solves the previously studied reduced kernel RPIE problem, and the other solves the more complicated exact kernel RPIE problem (for which there are no previous numerical results). Both algorithms behave stably for arbitrarily chosen values of the mesh size. Test experiments and numerically computed values of the induced current are presented.     

Enantio- and chemo-selective HPLC separations by chiral-achiral tandem-columns approach: the combination of CHIROBIOTIC TAG and SCX columns for the analysis of propionyl carnitine and related impurities

We describe a new tandem-columns chiral-achiral HPLC arrangement by using a chiral column (CHIROBIOTIC TAG) connected in series with an achiral column (Spherisorb S5 SCX), based on a strong cationic exchange mechanism; this approach is very useful for the analysis of chiral molecules, containing cationic groups in their structures. We used this special combination to develop an easy and convenient procedure for the enantio- and chemo-selective dosage of propionyl L-carnitine (1) and relative impurities (2-6), which allowed for the simultaneous separation and quantitation within 30 min. Under the best chromatographic conditions (acetonitrile-10 mM sodium dihydrogen phosphate 65:35, v/v (pHa 6.80) as the mobile phase and UV detection at 205 nm], all the individual peaks were well separated. The applicability of the method, fully validated, was demonstrated by the analysis of a pharmaceutical batch of propionyl L-carnitine, where we found the following contents: 98.5% for 1 (drug substance); 0.15% for 3; 0.1% for 5 and 0.2% for 6. The enantiomeric excess (e.e.%) measured for the drug substance was 98.9%. Finally, a single mixed-bed column, packed with a binary mixture of the chiral and achiral phases, in a 1:1 ratio, gave similar chromatographic results as the tandem-columns approach, and thus, offered an easy alternative solution to the separation of the considered mixture.     

High-sensitivity observation of dipolar exchange and NOEs between exchangeable protons in proteins by 3D solid-state NMR spectroscopy

A highly sensitive new 1H-detected 3D solid-state NMR method is described for characterizing 1H-1H spin exchange in nanocrystalline samples of 15N- and 2H-enriched protein. Long-range contacts are observed in human ubiquitin. The method is also used to show that numerous NOEs between backbone amides and crystal water protons can be observed.     

Synthesis of new ferrocenyl derivatives and their use in the first cyclopropanation of fullerene C60 with ferrocenes

New ferrocenyl derivatives (a β-ketoester and a β-diester) were synthesised and linked to fullerene C₆₀, with the aim to elucidate factors involved in intramolecular electronic communication. These are the first examples of fullerene functionalised with ferrocenes via the cyclopropanation reaction. The resulting dyads were characterised.     

Integration of parallel-operating quality systems

Since the 1980s, quality systems have become an essential element in successful companies and institutions. Today those systems are indispensable to fulfill the needs of the customers and last but not least the requirements of the society. Depending on the company's activities and fields of services, it is necessary to establish various quality systems. The Institut Fresenius (IF) Group runs a number of analytical laboratories and sampling groups. The whole group was accredited according to DIN EN 45001 in 1994. Good Laboratory Practice (GLP) was introduced in 1992 and was certified by the national authority. For certain customers, IF Group is also obliged to work according DIN EN ISO 9001 or GMP. A comparison of these systems with respect to their different priorities shows the possibility of integrating their rules into one comprehensive quality system. The IF Group has therefore installed a quality system operating in parallel. Multilocation accreditations and/or certifications are taking these efforts into account. The benefits are: high transparency of the system for the customers, auditors and personnel, a reduction of maintenance costs, and great flexibility to react to new standards. Could these activities lead to a new Integrated Management System?     

Polychlorinated androstanes from the burrowing sponge Cliona nigricans

Two new steroidal derivatives, named clionastatins A and B, have been isolated from the burrowing sponge Cliona nigricans. These molecules are tri-and tetrachlorinated androstane derivatives, respectively, and they represent the first polyhalogenated steroids found in a natural organism, either marine or terrestrial, and the first examples of halogenated androstanes in nature. Both clionastatins proved to be potently cytotoxic.