Methionine Methyl Ester Research Articles

Design, synthesis, characterization and evaluation of methionine-ABO based TSPO ligand

A novel series of molecules based on the acetamidobenzoxazolone (ABO) skeleton has been developed for diagnosing pathological conditions characterized by over-expression of the 18 kDa translocator protein (TSPO) in organs. To enhance the targeting of TSPO, methionine methyl ester was incorporated into the ABO structure, yielding ABMO 2-[2-(2-oxo-benzoxazol-3-yl)-acetylamino]-4-methylsulfanyl-butyric acid methyl ester, for potential biomedical applications. Two analogs, ABMO-Br and ABMO-Cl, with halogen substitutions at the 5th position of benzoxazolone, were designed and validated in silico for their pharmacokinetic properties, adherence to drug-like criteria, and blood-brain barrier penetration ability.Docking studies revealed the affinity of the designed molecules towards both native and mutant forms of TSPO. Based on in silico analysis, halogen derivatives were selected for synthesis. An efficient three-step synthetic procedure was employed to produce ABMO-Cl/Br, which were purified by column chromatography and characterized by NMR spectroscopy.The resultant ligands were radiolabeled with 99mTc, exhibiting significant stability in saline solution for up to 24 h. Blood kinetic studies conducted on New Zealand rabbits demonstrated substantial clearance from blood within 1 hr. Ex vivo and in vivo biodistribution studies confirmed uptake of the ligands in TSPO-rich organs. In conclusion, these studies validated the ability of these compounds to cross the blood-brain barrier in animal models. These findings underscore the potential of ABMO-Cl/Br as SPECT markers targeting TSPO. Further investigations using animal models are warranted to fully elucidate the utility of these ligands in diagnosing TSPO-related conditions.

Chiroptical and colorimetric switches based on helical polymer-metal nanocomposites prepared via redox metal translocation of helical polymer metal complexes.

A helical copoly(phenylacetylene) that follows a dynamic chiral accord effect has been designed to further synthesize dynamic chiral nanocomposites. Its two pendants are benzamides of (L)-methionine methyl ester [(L)-1, 20%] and (L)-alanine methyl ester [(L)-2, 80%], the former being responsible for binding the copolymer to metallic nanoparticles (MNPs, M = Au, Ag) via the thioether. The two chiral comonomers have analogous dynamic behavior, and therefore, the copolymer-poly-[(L)-10.2-co-(L)-20.8]-adopts a preferred helical sense that can be amplified or inverted by stimuli acting simultaneously on both pendants. The formation of nanocomposites can be followed by different sequential chiroptical responses of the copolymer once the helical polymer metal-complexes are formed-M to P helix inversion by the formation of poly-[(L)-10.2-co-(L)-20.8]/Au3+ or poly-[(L)-10.2-co-(L)-20.8]/Ag+-and further reduction with NaBH4 to generate the corresponding nanocomposites-P to M helix inversion by the formation of poly-[(L)-10.2-co-(L)-20.8]-AuNPs (6 nm) and poly-[(L)-10.2-co-(L)-20.8]-AgNPs (5 nm). These nanocomposites exhibit the properties of both components, helix inversion in the PPA and a colorimetric response in the MNPs triggered by metal ions.

Kinetics, mechanism and DFT calculations on base hydrolysis of -amino acid esters catalyzed by [Pd(TMPDA)(H2O)2]2+

Pd(TMPDA)Cl2 (TMPDA = N,N,N`,N`-tetramethyl-1,3-propanediamine) was synthesized and characterized by elemental analysis. [Pd(TMPDA)(H2O)2]2+ reacts with amino acid esters (L) to form mixed ligand [Pd(TMPDA)L]2+ complexes. The kinetics of base hydrolysis of [Pd(TMPDA)L]2+ was studied by pH-stat technique and the corresponding rate constants are reported. The coordinated glycine methyl ester is efficiently hydrolyzed, whereas the coordinated methionine methyl ester is hydrolysed with a much lower catalytic activity. The catalytic influence is depended on the mode of coordination of the ester to the palladium complex. Probable mechanisms for these reactions are considered. Activation parameters for the hydrolysis of the coordinated glycine methyl ester were determined experimentally. DFT calculations (B3LYP/LANL2DZ) were applied to determine the possible mechanism of the base hydrolysis of the amino acid esters. The calculations are discussed in reference to the reported experimental data.

New Differently Functionalized Cyclopentenediones

2-Allyl-2,4-dichloro-5-(2,4,6-trimethoxyphenyl)cyclopent-4-ene-1,3-dione reacted with highly nucleophilic secondary (diethylamine, morpholine, N-methylpiperazine, piperidine) and primary amines (allylamine) under mild conditions (methanol, 20°C, 24 h) to give products of substitution of the 4-chlorine atom in 60–87% yield. The reaction of the same compound with a weak nitrogen nucleophile, imidazole, afforded 4-(1H-imidazol-1-yl) derivative in a low yield (25%). Methionine methyl ester hydrochloride failed to react with 2-allyl-2,4-dichloro-5-(2,4,6-trimethoxyphenyl)cyclopent-4-ene-1,3-dione in methanolic potassium hydroxide; instead, 55% of 2-allyl-2-chloro-4-methoxy-5-(2,4,6-trimethoxyphenyl)cyclopent-4-ene-1,3-dione was obtained. The reaction with methyl 2-sulfanylacetate in the presence of sodium hydride produced methyl {[4-allyl-4-chloro-3,5-dioxo-2-(2,4,6-trimethoxyphenyl)cyclopent-1-en-1-yl]sulfanyl}acetate in 47% yield.

Synthesis, characterization, antimicrobial and antitumor reactivity of new palladium(II) complexes with methionine and tryptophane coumarine derivatives

In reaction of 3-acetyl-4-hydroxy coumarine with methionine methyl ester hydrochloride and tryptophane methyl ester hydrochloride the corresponding enamine ligands were obtained. Palladium (II) complexes were prepared in reaction of potassium-tetrachloridopalladate (II) and corresponding enamine. All compounds were characterized by microanalysis, infrared, 1H and 13C NMR spectroscopy. In vitro antitumor activity of the mentioned ligands and corresponding palladium (II) complexes, as well as me-Gly and me-Val ligands and [Pd (me-Gly)]Cl and [Pd (me-Val)2] complexes was determined by MTT assay against two leukemia cell lines (JVM-13 and MOLT-4) and against primary leukemic cells isolated from chronic lymphocytic leukemia (CLL) patients. Antimicrobial activity of the tested compound was evaluated by determining the minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) against three reference bacterial strains: E. faecalis, P. aeruginosa, S. aureus and one clinical isolate of yeast: Candida spp.

Synthesis of Methionine‐Derived Endocyclic Sulfilimines and Sulfoximines

The asymmetric synthesis of endocyclic methionine sulfilimines and sulfoximines from methionine derivatives was explored. The cyclization was performed by using phenyliodine diacetate (PIDA). In the case of l‐methionine, dehydromethionine was obtained, and a deprotonation step by tBuONa was necessary to yield the corresponding sulfilimine. On the other hand, the cyclic sulfilimine of methionine methyl ester, methylthiopropylamine, and l‐methioninol were synthesized in a single step by using PIDA. Owing to their instability, the sulfilimines were oxidized to their corresponding sulfoximines in good yields.

Base hydrolysis of α-amino acid esters catalysed by [Pd(N-ethylethylenediamine)(H2O)2]2+. Kinetic study and DFT calculations

Amino acid esters (L) react with [Pd(Eten)(H2O)2]2+ (Eten=N-ethyl ethylenediamine) giving mixed ligand complexes of the type [Pd(Eten)L]2+. Base hydrolysis of [Pd(Eten)L]2+ was studied by pH-stat technique from which rate constants for the base hydrolysis of the esters were obtained. The glycine methyl ester hydrolysed significantly, whereas the methionine methyl and histidine methyl esters hydrolysed much slower. The mode of coordination of the ester plays a role in the catalysis, and possible mechanisms for these reactions are considered. Activation parameters were determined for the hydrolysis of the glycine methyl ester. The effect of the dielectric constant of the medium on the hydrolysis process was also investigated. The B3LYP/LANL2DZ method was used for geometric optimization of the free ligand and the complex using the Gaussian 09 program. The calculations are compared with the kinetic data. In addition, the vibrational frequencies of the molecules were computed for the optimized geometries.

A “soft” ionization mass spectrometric study of organic sulfides as sulfonium salts

Preliminary conversion of nonpolar organic sulfides into sulfonium salts was proposed for their study and analysis by laser desorption/ionization (MALDI and SALDI) and electrospray/ionization (ESI) mass spectrometry. General possibilities of the methodology proposed were demonstrated on examples of dialkyl sulfides, substituted thiacyclanes, dibenzothiophene, and methionine methyl ester. Various alkyl and aralkyl halides, as well as trimethyl- and triethyloxonium salts were tested as alkylating agents. S-alkylation was shown to proceed quantitatively under mild conditions. MALDI and SALDI mass spectra (a matrix-free nanostructurized target was used in SALDI experiments) displayed only ion peaks corresponding to sulfonium cations whose mass numbers were equal to the sum of molecular weights of sulfides and weight increments of the introduced alkyl and aralkyl groups. Trans-alkylation was observed for benzyl-substituted sulfides. Tandem mass spectrometry provided preliminary data on the fragmentation of ESI-generated sulfonium cations and demonstrated differences in the MS/MS spectra of regioisomers.

Thermal stability of Pd(1,4-bis(2-hydroxyethyl)piperazine)Cl2 and its role in the catalysis of base hydrolysis of α-amino acid esters

Pd(BHEP)Cl2 was synthesized and characterized (BHEP = 1,4-bis(2-hydroxyethyl)piperazine). The complex decomposes in two steps, leaving a residue of palladium metal. Amino acid ester (L) reacts with [Pd(BHEP)(H2O)2]2+ (BHEP = 1,4-bis(2-hydroxyethyl)piperazine), giving mixed-ligand complexes, [Pd(BHEP)L]2+. The kinetics of hydrolysis of [Pd(BHEP)L]2+ have been studied by pH-stat technique, and rate constants were obtained. Rate acceleration observed for glycine methyl ester is high. The effect with methionine methyl ester is much less marked, as the mixed-ligand complexes with these ligands do not involve alkoxycarbonyl donors. Possible mechanisms for these reactions are considered.

Speciation studies of mono- and binuclear Pd(II) complexes involving mixed nitrogen–sulfur donor ligand and 4,4′-bipiperidine as a linker

Pd(MME)Cl2 complex, where MME = methionine methyl ester, was synthesized and characterized by elemental analysis and spectroscopic techniques. [Pd(MME)(H2O)2]2+ interacts with some DNA constituents giving 1 : 1 and 1 : 2 complexes. The binuclear complexes having 4,4′-bipiperidine as a linker and involving [Pd(MME)(H2O)2]2+ and DNA constituents were investigated. The results show formation of [(H2O)(MME)Pd(Bip)Pd(MME)(H2O)]4+. Inosine, uracil, and thymine interact with the previously mentioned complex by substitution of the two coordinated water molecules. Formation constants of all possible mono- and binuclear complexes were determined and their speciation diagrams were evaluated.

Palladium(II) Complexes Containing Mixed Nitrogen-Sulphur Donor Ligands: Interaction of [Pd(Methionine Methyl Ester)(H2O)2](2+) with Biorelevant Ligands.

Pd(MME)Cl2 complex (MME = methionine methyl ester) was synthesised and characterized by physicochemical measurements. The reaction of [Pd(MME)(H2O)2]2+ with amino acids, peptides, or dicarboxylic acids was investigated at 25°C and 0.1 M ionic strength. Amino acids and dicarboxylic acids form 1 : 1 complexes. Peptides form both 1 : 1 complexes and the corresponding deprotonated amide species. The stability of the complexes formed was determined and the binding centres of the ligands were assigned. Effect of solvent on the stability constant of Pd(MME)-CBDCA complex, taken as a representative example, shows that the complex is more favoured in a medium of low dielectric constant. The concentration distribution diagrams of the complexes were evaluated.

Synthesis of New Gold(I) Thiolates Containing Amino Acid Moieties with Potential Biological Interest

The reaction of the gold(I) complex [Au(SpyCOOH)(PPh3)], which contains nicotinic acid thiolate, with several amino acid esters such as glycine methyl ester or the enantiomerically pure L isomers of alanine methyl ester, phenylalanine methyl ester, valine methyl ester, methionine methyl ester, and proline methyl ester produces the gold(I) derivatives with the new thiolate containing amino acid ester ligands [Au{SpyCONHCH(R)COOMe}(PPh3)]. The reaction of these amino acid ester derivatives with LiOH in methanol and acidification with KHSO4 until pH 3-4 afford the corresponding acids, which are water-soluble species. These amino acid compounds can be further coupled with other amines, such as, for example, isopropylamine, to give the corresponding amide derivatives. The species with glycine methyl ester and valine methyl ester have been characterized by X-ray crystallography, showing, in the second case, only one of the enantiomers, which proves that retention of the configuration after reaction occurs.

Rapid Isolation of Lysosomal Membranes from Cultured Cells

We present a simple method for enrichment of lysosomal membranes from HEK293 and HeLa cell lines taking advantage of selective disruption of lysosomes by methionine methyl ester. Organelle concentrate from postnuclear supernatant was treated with 20 mmol/l methionine methyl ester for 45 min to lyse the lysosomes. Subsequently, lysosomal membranes were resolved on a step sucrose gradient. An enriched lysosomal membrane fraction was collected from the 20%/35% sucrose interface. The washed lysosomal membrane fraction was enriched 30 times relative to the homogenate and gave the yield of more than 8 %. These results are comparable to lysosomal membranes isolated by magnetic chromatography from cultured cells (Diettrich et al., 1998). The procedure effectively eliminated mitochondrial contamination and minimized contamination from other cell compartments. The enriched fractions retained the ability to acidify membrane vesicles through the activity of lysosomal vacuolar ATPase. The method avoids non-physiological overloading of cells with superparamagnetic particles and appears to be quite robust among the tested cell lines. We expect it may be of more general use, adaptable to other cell lines and tissues.

Kinetics and Mechanism for Hydrolysis of α-Amino Acid Esters in Mixed Ligand Complexes with Zn(II)–Nitrilo-tris(methyl phosphonic Acid)

The kinetics of base hydrolysis of the alanine ethyl ester, in addition to glycine, histidine and methionine methyl esters in the presence of the Zn-NTP complex, were studied in aqueous solution by the pH-potentiometric technique, where NTP denotes the nitrilo-tris(methyl phosphonic acid) ligand. The kinetic data fits assumed that hydrolysis proceeds through formation of a M–OH complex, followed by an intramolecular OH− attack. The effect of an organic solvent on the hydrolysis of coordinated esters was investigated by measuring the rate of hydrolysis in dioxane–water solutions of different compositions at t=25.0 °C and I=0.1 mol⋅dm−3. The kinetics of base hydrolysis of the glycine methyl ester was studied at different temperatures. Activation parameters for the base hydrolysis of the complexes were evaluated.

Farnesyltransferase Inhibitor FTI-277 Reduces Mortality of Septic Mice along with Improved Bacterial Clearance

Treatment with statins, inhibitors of HMG-CoA reductase, extends the survival of septic mice. However, the molecular mechanisms underlying the cholesterol-lowering, independent beneficial effects of statins in sepsis are poorly understood. The inhibition of protein isoprenylation, namely farnesylation and geranylgeranylation, has been proposed as a mediator of the pleiotropic protective effects of statins, although direct evidence is lacking. Major features of sepsis-induced immune suppression include T-cell dysfunction, which is characterized by apoptosis of splenic T cells, increased CD4(+)Foxp3(+) regulatory T cells (Tregs), and suppression of type 1 helper T-cell response [e.g., interferon-γ (IFN-γ) secretion] in mice. Here, we show that the induction of sepsis by cecal ligation and puncture (CLP) resulted in increases in farnesyltransferase activity and farnesylated proteins in the spleen relative to sham operation. Treatment with farnesyltransferase inhibitor N-[4-[2(R)-amino-3-mercaptopropyl]amino-2-phenylbenzoyl]methionine methyl ester trifluoroacetate salt (FTI-277) (25 mg/kg b.wt. i.p.) at 2 h after CLP blocked the increase in farnesylated proteins and improved survival and bacterial clearance of septic mice. FTI-277 reverted to or mitigated sepsis-induced apoptosis in spleen and thymus, increased splenic CD4(+)Foxp3(+) Tregs, and suppressed IFN-γ secretion and proliferation of splenocytes in response to anti-CD3+CD28 antibodies in mice. Moreover, FTI-277 promoted macrophage phagocytotic activity in septic mice. These results indicate that elevation in protein farnesylation plays a role in derangements in immune function and mortality of septic mice. These findings suggest that prevention of immune dysfunction might contribute to FTI-277-induced improvement in survival of septic mice. These data highlight protein farnesyltransferase as a novel potential molecular target to reduce the mortality of patients with sepsis.

The Palladium(Ii)-Picolylamine Promoted Hydrolysis of Amino Acid Esters; Kinetic Evidence for Inter- and Intramolecular Mechanisms

The hydrolysis of amino acid esters is catalysed by the palladium(II) complex [Pd(Pic)]2+ (Pic = 2-picolylamine). The reaction has been studied by the pH-stat technique. The overall PdII chelate-promoted hydrolysis of the ethyl esters of glycine and alanine may be accounted by inter-and intramolecular mechanisms depicted in Eqns (1) and (2) respectively. [Formula: see text] (1) [Formula: see text] (2) The kinetic data for histidine and methionine methyl esters are fitted assuming that hydrolysis proceeds solely by the intermolecular mechanism [Eqn (1)]. The rate enhancement compared with the free ester is discussed in terms of the structure of the complex. Activation parameters associated with the hydrolysis have been determined and discussed.

Conjugates of ferrocene with biological compounds. Coordination to gold complexes and antitumoral properties

Several bioconjugates of ferrocene with biological compounds such as aminoacid esters and related species have been prepared by reaction of chlorocarbonyl ferrocene with the corresponding amino acid ester (histidine methyl ester, tryptophan methyl ester, methionine methyl ester and lysine ethyl ester) or histamine or prolinamide in the presence of NEt 3. The reaction of the tryptophan or prolinamide ferrocene conjugates with [Au(acac)(PR 3)] (acac = acetylacetonate) results in the substitution of the proton of the cyclic NH groups by the fragment AuPR 3 + affording the complexes [Au(FcCO-tryptophan-OMe)(PR 3)] or [Au(FcCO-prolinamide)(PR 3)] (Fc = ferrocenyl group). The reaction of FcCO-Met-OMe with [Au(OTf)(PR 3)] (OTF = trifluoromethysulfonate) or [Au(C 6F 5) 3(OEt 2)] yields the gold(I) or gold(III) derivatives [Au(FcCO-Met-OMe)(PR 3)]OTf or [Au(C 6F 5) 3(FcCO-Met-OMe)], respectively. Cytotoxicity studies towards several cancer lines such as MCF-7, HeLa or NIE-115 have been performed. The ferrocene bioconjugates show no activity whereas the gold complexes exhibit antiproliferative effect. Preliminary studies of interaction of compounds with cells were carried out with the goal of increasing our knowledge on the mechanism of action of these potential drugs.

Tipifarnib-Induced Apoptosis in Acute Myeloid Leukemia and Multiple Myeloma Cells Depends on Ca2+Influx through Plasma Membrane Ca2+Channels

A major contributing factor to the high mortality rate associated with acute myeloid leukemia and multiple myeloma is the development of resistance to chemotherapy. We have shown that the combination of tipifarnib, a nonpeptidomimetic farnesyltransferase inhibitor (FTI), with bortezomib, a proteosome inhibitor, promotes synergistic death and overcomes de novo drug resistance in acute myeloid leukemia cell lines. Experiments were undertaken to identify the molecular mechanisms by which tipifarnib produces cell death in acute myeloid leukemia and multiple myeloma cell lines (U937 and 8226, respectively). Tipifarnib, but not other FTIs tested [N-[4-[2(R)-amino-3-mercaptopropyl]amino-2-phenylbenzoyl]methionine methyl ester trifluoroacetate salt (FTI-277) and 2'-methyl-5-((((1-trityl-1H-imidazol-4-yl)methyl)amino)methyl)-[1,1'-biphenyl]-2-carboxylic acid (FTI-2153), promotes elevations in intracellular free-calcium concentrations ([Ca(2+)](i)) in both cell lines. These elevations in [Ca(2+)](i) were accompanied by highly dynamic plasmalemmal blebbing and frequently resulted in membrane lysis. The tipifarnib-induced elevations in [Ca(2+)](i) were not blocked by thapsigargin or ruthenium red, but were inhibited by application of Ca(2+)-free extracellular solution and by the Ca(2+) channel blockers Gd(3+) and La(3+). Conversely, 2-aminoethoxydiphenyl borate (2-APB) potentiated the tipifarnib-evoked [Ca(2+)](i) overload. Preventing Ca(2+) influx diminished tipifarnib-evoked cell death, whereas 2-APB potentiated this effect, demonstrating a link between tipifarnib-induced Ca(2+) influx and apoptosis. These data suggest that tipifarnib exerts its effects by acting on a membrane channel with pharmacological properties consistent with store-operated channels containing the Orai3 subunit. It is noteworthy that Orai3 transcripts were found to be expressed at lower levels in tipifarnib-resistant 8226/R5 cells. Our results indicate tipifarnib causes cell death via a novel mechanism involving activation of a plasma membrane Ca(2+) channel and intracellular Ca(2+) overload.

Paracetamol (Acetaminophen) Decreases Hydrogen Sulfide Tissue Concentration in Brain but Increases It in the Heart, Liver and Kidney in Mice

The biological action ofN-acetyl-p-aminophenol - paracetamol (acetaminophen) has been demonstrated to involve different mechanisms and is still not clear. Hydrogen sulfide (H2S) has been shown to play an important role in many physiological and pathological processes including nociception. The interaction between acetaminophen and endogenous H2S is unknown. Twenty four female CBA strain mice were administered intraperitoneal injections of N-acetyl-p-aminophenol solution: paracetemol in doses of 30 mg/kg b.w. per day (group D1, n = 8) or 100 mg/kg b.w. per day (group D2, n = 8).. The control group (n = 8) received physiological saline in portions of the same volume--0.2 ml. The measurements of tissue H2S concentration were performed with the Siegel spectrophotometric modified method. In the brain, the H2S tissue level decreased, but more significantly in the lower drug dose group. Conversely, there was a significant rise in the H2S tissue concentration in D1 and D2 groups in heart and kidney with the increase more pronounced in the group with the lower paracetamol dose. In the liver only the higher acetaminophen dose elicited a change in H2S concentration, increasing after administration of acetaminophen at 100 mg/kg. Our study demonstrates that paracetamol induces H2S tissue concentration changes in different mouse organs.

Adducts of rhodium(II) tetraacylates with methionine and its derivatives: 1H and 13C nuclear magnetic resonance spectroscopy and chiral recognition

Complexation of rhodium(II) dimeric tetraacylates: tetraacetate Rh 2AcO 4, tetratrifluoroacetate Rh 2TFA 4 , and ( S)-Mosher’s acid salt Rh 2MTPA 4 with both enantiomerically pure and racemic methionine and its derivatives: hydrochloric salt of methionine, hydrochloric salt of methionine methyl ester, N-formyl methionine, N-phthaloyl methionine, N-phthaloyl methyl ester of methionine, and methyl ester of N, N-dimethylmethionine has been investigated by means of 1H and 13C nuclear magnetic resonance ( 1H and 13C NMR) and absorption electronic spectroscopy in the visible range. Complexation processes were investigated in D 2O or CDCl 3 solutions, depending on the ligands’ and rhodium salts’ solubilities. Some supporting measurements were performed in the solid phase, using 13C and 15N CPMAS NMR techniques. All ligands investigated form 1:1 and 1:2 adducts in the solution, depending on the rhodium salt to ligand molar ratios. The complexation site in the ligands (S atom) was deduced on the basis of the NMR parameter adduct formation shift (Δ δ = δ adduct − δ ligand) and calculated chemical shifts (DFT, NMR GIAO). In the cases of the Rh 2TFA 4 and Rh 2MTPA 4 adducts, decreasing the temperature within the range 220–254 K slowed down the ligand exchange and allowed us to observe the signals of all diastereoisomers in the 1H and 13C NMR spectra.