Ab initio study of the binding of Trichostatin A (TSA) in the active site of histone deacetylase like protein (HDLP)

Histone deacetylase (HDAC) inhibitors have recently attracted considerable interest because of their therapeutic potential for the treatment of cell proliferative diseases. An X-ray structure of a very potent inhibitor, Trichostatin A (TSA), bound to HDLP (an HDAC analogue isolated from Aquifex aeolicus), is available. From this structure, an active site model (322 atoms), relevant for the binding of TSA and structural analogues, has been derived, and TSA has been minimized in this active site at HF 3-21G* level. The resulting conformation is in excellent accordance with the X-ray structure, and indicates a deprotonation of the hydroxamic acid in TSA by His 131. Also, a water molecule was minimized in the active site. In addition to a similar deprotonation, in accordance with a possible catalytic mechanism of HDAC as proposed by Finnin et al. (M. S. Finnin, J. R. Donigian, A. Cohen, V. M. Richon, R. A. Rifkind and P. A. Marks, Nature, 1999, 401, 188-193), a displacement of the resulting OH- ion in the active site was observed. Based on these results, the difference in energy of binding between TSA and water was calculated. The resulting value is realistic in respect to experimental binding affinities. Furthermore, the mechanism of action of the His 131-Asp 166 charge relay system was investigated. Although the Asp residue in this motif is known to substantially increase the basicity of the His residue, no proton transfer from His 131 to Asp 166 was observed on binding of TSA or water. However, in the empty protonated active site, this proton transfer does occur.     

Amidinoethylation—a new reaction—IV : The amidinoethylation of alcohols: a facile synthesis of 3-alkoxy-N,N'-substituted-propanamidines

The amidinoethylation of alcohols takes place by the addition of sodium alkoxides 2 (R¹ = Me, Et) to the CC double bond of a variety of N,N'-substituted-propenamidines 1 (Method A). This illustrates the activation of the CC double bond by the conjugated amidine function and provides a new class of Michael acceptors for alcohols. However, this activation is poorer than with other nucleophiles or Michael acceptors. The amidinoethylation makes available 3-alkoxy-N,N'-substituted-amidines not easily accessible by other classical methods. However, it is demonstrated that the general N,N'-substituted-amidine synthesis via the nitrilium salts can also apply to nitrile compounds having an alkoxygroup present on the molecule (method B). Since the cyanoethylation of alcohols (4) is a very fast and facile reaction the method B is the preferred strategy for the synthesis of 3-alkoxy-N,N'-substituted-propanamidines 3.     

Strategies for multi-site GLP studies

 A GLP study can be performed at more than one site. This is called a multi-site study. Although, the study is performed at different sites, it is still one study and must completely comply with the GLP principles. The fact that different activities are conducted at different sites implies that the planning, the organization and the communication are crucial for the success of the study. This means that all the staff involved should know their responsibilities and should have the knowledge and skills to realize all the phases of the study according to the GLP principles. To achieve a well managed multi-site study, several strategies for setting up such a study can be followed. This paper focuses on the responsibilities, communication, and collaboration of the personnel, which are involved in a multi-site study. Several case studies are highlighted, and we concluded that the basic communication triangle in a single-site GLP study between test facility management, study director, and the quality assurance unit should be extended to the communication among test facility and test site management, study director, principle investigator(s), and the quality assurance units at the test sites. Introduction Received: 14 August 2002 Accepted: 26 November 2002     

A microwave-assisted click chemistry synthesis of 1,4-disubstituted 1,2,3-triazoles via a copper(I)-catalyzed three-component reaction

A microwave-assisted three-component reaction was used to prepare a series of 1,4-disubstituted-1,2,3-triazoles from corresponding alkyl halides, sodium azide, and alkynes. This procedure eliminates the need to handle organic azides, as they are generated in situ, making this already powerful click process even more user-friendly and safe.     

Occurrence of chain folding in micelles : A C NMR relaxation and photophysical study

¹³CT₁ relaxation times for the different carbons of the sodium dodecyl sulphate chain in micellar systems have been measured, using Gd³⁺ as a paramagnetic relaxation reagent. The fluorescence decay of ω-(-naphthyl) dodecanoic acid, solubflized in the sodium dodecyl sulphate micelles was obtained in the presence of various amounts of counterion quencher Both series of experiments point to the occurrence of chain folding and to the fact that the terminal group can approach the Stern region of the micelle.     

Mass spectrometric analysis of ceramide perturbations in brain and fibroblasts of mice and human patients with peroxisomal disorders

In this study, the levels and composition of ceramides in brains of newborn mice lacking peroxisomes (Pex5-/-, Zellweger mice) were analyzed using normal-phase high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (HPLC/APCI-MS). Total ceramide compositions were found to be comparable to that of control animals. However, a minor ceramide species, containing hexacosanoic/hexacosenoic acid as the amide fatty acid, was 9-fold increased. Also, in the sphingomyelin-derived ceramides this species was elevated. Subsequent analysis of extracts from fibroblasts of Pex5-/- mice and mice with a defective peroxisomal beta-oxidation (lacking D-specific multifunctional protein 2 (MFP2)), revealed, again, a similar rise in this particular ceramide. Further, this ceramide was elevated in human X-ALD fibroblasts as well. Whether C26:1/0-ceramide is linked to some of the pathology seen in Zellweger syndrome remains to be investigated. However, an increase in this sphingolipid can be considered as a diagnostic criterion for diseases caused by defects in peroxisome biogenesis or peroxisomal beta-oxidation.     

Perfluormethyl-Element-Liganden. XXIX. Darstellung und spektroskopische Untersuchungen von M(CO)4L2-Komplexen (M = Cr,Mo, W; L = Me2PSMe,Me2PSeMe, (CF3)2PSMe, (CF3)2PSeMe)

Perfluoromethyl Element Ligands. XXIX. Preparation and Spectroscopic Investigation of M(CO)₄L₂ Complexes (M ? Cr, Mo, W; L ? Me₂PSMe, Me₂PSeMe, (CF₃)₂PSMe, (CF₃)₂PSMe) The complexes M(CO)₄L₂ (see Inhaltsübersicht) have been prepared by the reaction of tetracarbonyl norbornadiene metal compounds M(CO)₄NBD with L at room temperature or 35°C, respectively. The cis-complexes formed in the first step undergo rearrangement to trans-isomers at higher temperatures. New compounds have been characterized by analytical and spectroscopic (IR, NMR, MS) methods.     

In viva PHOTODYNAMIC EFFECTS OF PHTHALOCYANINES IN A SKIN-FOLD OBSERVATION CHAMBER MODEL: ROLE OF CENTRAL METAL ION AND DEGREE OF SULFONATION

Six sulfonated metallophthalocyanines, chelated with either aluminum or zinc and sulfonated to different degrees, were studied in vivo for their photodynamic activity in a rat skin-fold chamber model. The chamber, located on the back of female WAG/Rij rats, contained a syngeneic mammary carcinoma implanted into a layer of subcutaneous tissue. Twenty-four hours after intravenous administration of 2.5 μmol/kg of one of the dyes, the chambers received a treatment light dose of 600 J/cm² with monochromatic light of 675 nm at a power density of 100 mW/ cm². During light delivery and up to a period of 7 days after treatment, vascular effects of tumor and normal tissue were scored. Tumor cell viability was determined by histology and by reimplantation of the chamber contents into the skin of the same animal, either 2 h after treatment or after the 7 day observation period. Vascular effects of both tumor and subcutaneous tissue were strongest with dyes with the lowest degree of sulfonation and decreased with increasing degree of sulfonation. Tumor regrowth did not occur with aluminum phthalocyanine mono- and disulfonate and with zinc phthalocyanine monosulfonate. With the protocol that was used, complete necrosis without recovery was only observed when reimplantation took place at the end of the 7 day follow-up period. Reimplantation 2 h after treatment always resulted in tumor regrowth. At this interval, the presence of viable tumor cells was confirmed histologically. In general tumor tissue vasculature was more susceptible to photodynamic damage than vasculature of the normal tissue. The effect on the circulation of both tumor and normal tissue increased with decreasing degree of sulfonation. Based on this study, the photodynamic effects using the six sulfonated metallophthalocyanines on the vasculature can be ranked from high to low as: AlPcS₂= ZnPcS₁ > AIPcS₁ > AIPcS₄ > ZnPcS₂ > ZnPcS₄.     

A study of the mechanism of response of liquid ion exchanger calcium selective electrodes: Part III. Membrane behaviour under non-zero current conditions

The I-E response of the liquid membrane of the calcium selective electrode is studied under constant or linearly varying current and voltage. An increase in the membrane resistance, recorded when an electrical current crosses the membrane, is due to the outflow of Cl^? ions initially present in the membrane. When calcium ions are replaced by alkaline ions inside the membrane at constant current, the decrease of the membrane resistance due to an ion exchange is in agreement with the conductivity measurements (Part II). When the applied voltage is imposed besides the ion exchange one must take into account the interfacial overpotential to explain the important rectification effect observed. The interfacial transfer constant rate of alkaline ions seems greater than that of Ca²⁺ ion.