Supramolecular synthon hierarchy in cyclopropyl-containing peptide-derived compounds

Recognizing the increasing importance of cyclopropyl containing peptide-derived compounds in the pharma industry, here we report the crystal engineering of a series of novel derivatives, i.e. diethyl 2-acetamido-2-(cyclopropylmethyl)malonate (1), 2-(cyclopropylmethyl)-2-acetamidopropanedioic...

The First Insight Into the Supramolecular System of D,L-α-Difluoromethylornithine: A New Antiviral Perspective

Targeting the polyamine biosynthetic pathway by inhibiting ornithine decarboxylase (ODC) is a powerful approach in the fight against diverse viruses, including SARS-CoV-2. Difluoromethylornithine (DFMO, eflornithine) is the best-known inhibitor of ODC and a broad-spectrum, unique therapeutical agent. Nevertheless, its pharmacokinetic profile is not perfect, especially when large doses are required in antiviral treatment. This article presents a holistic study focusing on the molecular and supramolecular structure of DFMO and the design of its analogues toward the development of safer and more effective formulations. In this context, we provide the first deep insight into the supramolecular system of DFMO supplemented by a comprehensive, qualitative and quantitative survey of non-covalent interactions via Hirshfeld surface, molecular electrostatic potential, enrichment ratio and energy frameworks analysis visualizing 3-D topology of interactions in order to understand the differences in the cooperativity of interactions involved in the formation of either basic or large synthons (Long-range Synthon Aufbau Modules, LSAM) at the subsequent levels of well-organized supramolecular self-assembly, in comparison with the ornithine structure. In the light of the drug discovery, supramolecular studies of amino acids, essential constituents of proteins, are of prime importance. In brief, the same amino-carboxy synthons are observed in the bio-system containing DFMO. DFT calculations revealed that the biological environment changes the molecular structure of DFMO only slightly. The ADMET profile of structural modifications of DFMO and optimization of its analogue as a new promising drug via molecular docking are discussed in detail.

A Global Review on Short Peptides: Frontiers and Perspectives

Peptides are fragments of proteins that carry out biological functions. They act as signaling entities via all domains of life and interfere with protein-protein interactions, which are indispensable in bio-processes. Short peptides include fundamental molecular information for a prelude to the symphony of life. They have aroused considerable interest due to their unique features and great promise in innovative bio-therapies. This work focusing on the current state-of-the-art short peptide-based therapeutical developments is the first global review written by researchers from all continents, as a celebration of 100 years of peptide therapeutics since the commencement of insulin therapy in the 1920s. Peptide "drugs" initially played only the role of hormone analogs to balance disorders. Nowadays, they achieve numerous biomedical tasks, can cross membranes, or reach intracellular targets. The role of peptides in bio-processes can hardly be mimicked by other chemical substances. The article is divided into independent sections, which are related to either the progress in short peptide-based theranostics or the problems posing challenge to bio-medicine. In particular, the SWOT analysis of short peptides, their relevance in therapies of diverse diseases, improvements in (bio)synthesis platforms, advanced nano-supramolecular technologies, aptamers, altered peptide ligands and in silico methodologies to overcome peptide limitations, modern smart bio-functional materials, vaccines, and drug/gene-targeted delivery systems are discussed.

A Proline-Based Tectons and Supramolecular Synthons for Drug Design 2.0: A Case Study of ACEI

Proline is a unique, endogenous amino acid, prevalent in proteins and essential for living organisms. It is appreciated as a tecton for the rational design of new bio-active substances. Herein, we present a short overview of the subject. We analyzed 2366 proline-derived structures deposited in the Cambridge Structure Database, with emphasis on the angiotensin-converting enzyme inhibitors. The latter are the first-line antihypertensive and cardiological drugs. Their side effects prompt a search for improved pharmaceuticals. Characterization of tectons (molecular building blocks) and the resulting supramolecular synthons (patterns of intermolecular interactions) involving proline derivatives, as presented in this study, may be useful for in silico molecular docking and macromolecular modeling studies. The DFT, Hirshfeld surface and energy framework methods gave considerable insight into the nature of close inter-contacts and supramolecular topology. Substituents of proline entity are important for the formation and cooperation of synthons. Tectonic subunits contain proline moieties characterized by diverse ionization states: -N and -COOH(-COO-), -N+ and -COOH(-COO-), -NH and -COOH(-COO-), -NH+ and -COOH(-COO-), and -NH2+ and -COOH(-COO-). Furthermore, pharmacological profiles of ACE inhibitors and their impurities were determined via an in silico approach. The above data were used to develop comprehensive classification, which may be useful in further drug design studies.

Synthesis, experimental and in silico studies of N-fluorenylmethoxycarbonyl-O-tert-butyl-N-methyltyrosine, coupled with CSD data: a survey of interactions in the crystal structures of Fmoc-amino acids

Recently, fluorenylmethoxycarbonyl (Fmoc) amino acids (e.g. Fmoc-tyrosine or Fmoc-phenylalanine) have attracted growing interest in biomedical research and industry, with special emphasis directed towards the design and development of novel effective hydrogelators, biomaterials or therapeutics. With this in mind, a systematic knowledge of the structural and supramolecular features in recognition of those properties is essential. This work is the first comprehensive summary of noncovalent interactions combined with a library of supramolecular synthon patterns in all crystal structures of amino acids with the Fmoc moiety reported so far. Moreover, a new Fmoc-protected amino acid, namely, 2-{[(9H-fluoren-9-ylmethoxy)carbonyl](methyl)amino}-3-{4-[(2-hydroxypropan-2-yl)oxy]phenyl}propanoic acid or N-fluorenylmethoxycarbonyl-O-tert-butyl-N-methyltyrosine, Fmoc-N-Me-Tyr(t-Bu)-OH, C₂₉H₃₁NO₅, was successfully synthesized and the structure of its unsolvated form was determined by single-crystal X-ray diffraction. The structural, conformational and energy landscape was investigated in detail by combined experimental and in silico approaches, and further compared to N-Fmoc-phenylalanine [Draper et al. (2015). CrystEngComm, 42, 8047-8057]. Geometries were optimized by the density functional theory (DFT) method either in vacuo or in solutio. The polarizable conductor calculation model was exploited for the evaluation of the hydration effect. Hirshfeld surface analysis revealed that H...H, C...H/H...C and O...H/H...O interactions constitute the major contributions to the total Hirshfeld surface area in all the investigated systems. The molecular electrostatic potentials mapped over the surfaces identified the electrostatic complementarities in the crystal packing. The prediction of weak hydrogen-bonded patterns via Full Interaction Maps was computed. Supramolecular motifs formed via C-H...O, C-H...π, (fluorenyl)C-H...Cl(I), C-Br...π(fluorenyl) and C-I...π(fluorenyl) interactions are observed. Basic synthons, in combination with the Long-Range Synthon Aufbau Modules, further supported by energy-framework calculations, are discussed. Furthermore, the relevance of Fmoc-based supramolecular hydrogen-bonding patterns in biocomplexes are emphasized, for the first time.

A Supramolecular Approach to Structure-Based Design with A Focus on Synthons Hierarchy in Ornithine-Derived Ligands: Review, Synthesis, Experimental and in Silico Studies

The success of innovative drugs depends on an interdisciplinary and holistic approach to their design and development. The supramolecular architecture of living systems is controlled by non-covalent interactions to a very large extent. The latter are prone to extensive cooperation and like a virtuoso play a symphony of life. Thus, the design of effective ligands should be based on thorough knowledge on the interactions at either a molecular or high topological level. In this work, we emphasize the importance of supramolecular structure and ligand-based design keeping the potential of supramolecular H-bonding synthons in focus. In this respect, the relevance of supramolecular chemistry for advanced therapies is appreciated and undisputable. It has developed tools, such as Hirshfeld surface analysis, using a huge data on supramolecular interactions in over one million structures which are deposited in the Cambridge Structure Database (CSD). In particular, molecular interaction surfaces are useful for identification of macromolecular active sites followed by in silico docking experiments. Ornithine-derived compounds are a new, promising class of multi-targeting ligands for innovative therapeutics and cosmeceuticals. In this work, we present the synthesis together with the molecular and supramolecular structure of a novel ornithine derivative, namely N-α,N-δ)-dibenzoyl-(α)-hydroxymethylornithine, 1. It was investigated by modern experimental and in silico methods in detail. The incorporation of an aromatic system into the ornithine core induces stacking interactions, which are vital in biological processes. In particular, rare C=O…π intercontacts have been identified in 1. Supramolecular interactions were analyzed in all structures of ornithine derivatives deposited in the CSD. The influence of substituent was assessed by the Hirshfeld surface analysis. It revealed that the crystal packing is stabilized mainly by H…O, O…H, C…H, Cl (Br, F)…H and O…O interactions. Additionally, π…π, C-H…π and N-O…π interactions were also observed. All relevant H-bond energies were calculated using the Lippincott and Schroeder H-bond model. A library of synthons is provided. In addition, the large synthons (Long-Range Synthon Aufbau Module) were considered. The DFT optimization either in vacuo or in solutio yields very similar molecular species. The major difference with the relevant crystal structure was related to the conformation of terminal benzoyl C15-C20 ring. Furthermore, in silico prediction of the extensive physicochemical ADME profile (absorption, distribution, metabolism and excretion) related to the drug-likeness and medicinal chemistry friendliness revealed that a novel ornithine derivative 1 has the potential to be a new drug candidate. It has shown good in silico absorption and very low toxicity.

May warfarin prevent cancer?

Animal and epidemiologic studies suggest that the use of warfarin might reduce cancer incidence. The antitumor potential of warfarin is demonstrated in different experimental cancer models. Specifically, studies in murine cancer models have shown that warfarin blocks AXL receptor tyrosine kinase by inhibiting a vitamin K-dependent protein called GAS6, thereby may halt the spread of cancer cells. An off-target effect of the anticoagulant warfarin is inhibition of GAS6-AXL signaling, which enhances antitumor immunity and blocks tumorigenesis independently of anticoagulation. Hence, the observed association between warfarin use and lower cancer incidence is likely due to an enhanced antitumor immune surveillance of early cancer. The large observational study also showed a reduction in cancer incidence among regular warfarin users. The study data indicate that warfarin provides a possible cancer protection. Despite some limitations, the results of this study give further support for the hypothesis that warfarin use decreases cancer incidence, which warrants continued investigation. This finding may have important implications for choosing medications in patients who need anticoagulant therapy.

Modelling of absorption, distribution and physicochemical properties of AT1 receptor antagonists / Modelovanie absorpcie, distribúcie a fyzikálnochemických vlastnosti antagonistov AT1 receptorov

The theoretical chemistry methods were used to elucidate absorption, distribution and physicochemical properties of AT1 receptor antagonists and dual angiotensin II and endothelin A receptor antagonist (PS-433540). Computed partition coefficients (ALOGPS method) studied for drugs varied between 2.98 and 6.66. Neutral compounds are described as lipophilic drugs. Telmisartan is a drug with the highest lipophilicity. The neutral forms of the studied AT1 receptor antagonists are practically insoluble in water, and their computed solubilities is in interval between 2.04 and 22.65 mg/l (ALOGpS method). The calculated pKa values for tetrazolyle moiety are in the range 3.92-5.00 and for carboxylic moiety 3.12-5.50. Telmisartan (polar surface area = 72.95 A) and irbesartan (polar surface area = 87.14 A) belong to the AT1 receptor antagonists with increased absorption.

[Are we to pay attention to factor XII deficiency?]

Severe coagulation factor XII (FXII) deficiency is a very rare, mysterious and not well known inherited condition. Unlike other coagulation factor deficiencies, it is totally asymptomatic. Surprisingly, it does not lead to abnormal bleeding, even with major surgical procedures. The explanation for the lack of bleeding manifestations is unknown. It is suggested, but unproven, that patients are not sufficiently protected from thrombosis. FXII deficiency is usually discovered by accident through a routine coagulation testing done prior to surgery. Since FXII plays an important role in clot formation during in vitro measurements, its deficiency causes a marked prolongation of the activated partial thromboplastin time in the laboratory examination. The main concern related to FXII deficiency is the unnecessary testing, delay in health care and worry of surgical interventions that may be prompted by the abnormal laboratory result.

Captopril and its dimer captopril disulfide: comparative structural and conformational studies

The crystal structures of captopril {systematic name: (2S)-1-[(2S)-2-methyl-3-sulfanylpropanoyl]pyrrolidine-2-carboxylic acid}, C(9)H(15)NO(3)S, (1), and its dimer disulfide metabolite, 1,1'-{disulfanediylbis[(2S)-2-methyl-1-oxopropane-3,1-diyl]}bis-L-proline, C(18)H(28)N(2)O(6)S(2), (2), were determined by single-crystal X-ray diffraction analysis. Compound (1) crystallizes in the orthorhombic space group P2(1)2(1)2(1), while compound (2) crystallizes in the monoclinic space group P2(1), both with one molecule per asymmetric unit. The molecular geometries of (1) and (2) are quite similar, but certain differences appear in the conformations of the five-membered proline rings and the side chains containing the sulfhydryl group. The proline ring adopts an envelope conformation in (1), while in (2) it exists in envelope and slightly deformed half-chair conformations. The conformation adopted by the side chain is extended in (1) and folded in (2). A minimum-energy conformational search using Monte Carlo methods in the aqueous phase reveals that the optimized conformations of the title compounds differ from those determined crystallographically, which depend on their immediate environment. Intermolecular O-H...O and relatively weak C-H...O interactions seem to be effective in both structures and, together with S-H...O and C-H...S contacts, they create three-dimensional networks.

[Are we to pay attention to factor XII deficiency?]

Severe coagulation factor XII (FXII) deficiency is a very rare, mysterious and not well known inherited condition. Unlike other coagulation factor deficiencies, it is totally asymptomatic. Surprisingly, it does not lead to abnormal bleeding, even with major surgical procedures. The explanation for the lack of bleeding manifestations is unknown. It is suggested, but unproven, that patients are not sufficiently protected from thrombosis. FXII deficiency is usually discovered by accident through a routine coagulation testing done prior to surgery. Since FXII plays an important role in clot formation during in vitro measurements, its deficiency causes a marked prolongation of the activated partial thromboplastin time in the laboratory examination. The main concern related to FXII deficiency is the unnecessary testing, delay in health care and worry of surgical interventions that may be prompted by the abnormal laboratory result.

KEY WORDS

activated partial thromboplastin time - bleeding - blood coagulation - factor XII.

A comparative study of the molecular structure, lipophilicity, solubility, acidity, absorption and polar surface area of coumarinic anticoagulants and direct thrombin inhibitors

The methods of computational chemistry have been used to elucidate the molecular properties of coumarinic anticoagulants (acenocoumarol, phenprocoumon, warfarin and tecarfarin) and direct thrombin inhibitors (melagatran, dabigatran and their prodrug forms).

An orthorhombic polymorph of a cyclization product of perindopril

Low-temperature X-ray diffraction experiments were employed to investigate the crystal structures of an orthorhombic polymorph of the intramolecular cyclization product of perindopril, a popular angiotensive-converting enzyme (ACE) inhibitor, namely ethyl (2S)-2-[(3S,5aS,9aS,10aS)-3-methyl-1,4-dioxo-5a,6,7,8,9,9a,10,10a-octahydro-3H-pyrazino[1,2-a]indol-2-yl]pentanoate, C19H30N2O4, (Io), and its tetragonal equivalent, (It), which was previously reported at ambient temperature [Bojarska et al. (2013). J. Chil. Chem. Soc. 58, 1415-1417]. Polymorph (Io) crystallizes in the orthorhombic space group P2(1)2(1)2(1) with two molecules in the asymmetric unit, while tetragonal form (It) crystallizes in the space group P4(1)2(1)2 with one molecule in the asymmetric unit. The geometric parameters of (Io) are very similar to those of (It). The six-membered rings in both polymorphs adopt a slightly deformed chair conformation and the piperazinedione rings are in a boat conformation. However, the proline rings adopt an envelope conformation in (Io), while in (It) the ring exists in a slightly deformed half-chair conformation. The most significant difference between the two structures is the orientation of the ethyl pentanoate chain. Molecules associate in pairs in a head-to-tail manner forming infinite columns. In (Io), molecules are related by a twofold screw axis forming identical columns, while in (It), molecules in successive neighbouring columns are related by alternating twofold screw axes and fourfold screw axes. In both cases, the crystal packing is stabilized by weak intermolecular C-H···O interactions only.

[Is antiplatelet therapy always effective?]

OBJECTIVE

Acetylsalicylic acid (ASA) and clopidogrel (KLP) therapy is associated with the high degree of variability in response to the drug and some patients are drug-resistant. The aim of our study was to evaluate the individual response to antiplatelet therapy in patients at high risk of cardiovascular events treated with ASA (n = 131), KLP (n = 51) or ASA + KLP (n = 34).

SUBJECTS AND METHODS

Investigations were performed in them by light transmission aggregometry and in selected patients by VASP fosforylation.

RESULTS

Good response to ASA treatment with arachidonic acid-induced platelet aggregation inhibition < 20% reached 75.0% of patients, partial response with 20-40% inhibition 12.9% of patients and poor response with > 40 % inhibition 12.1 % of patients. Good response to KLP treatment with 20 µmol/l ADP-induced platelet aggregation inhibition < 60% reached 66.1% of patients, partial response with 60-70% inhibition 13.9% of patients and poor response > 70% in 20% of patients. In patients treated by KLP + ADP induced platelet aggregation correlated with VASP fosforylation. We found, that 50% of KLP-treated and 44.4% of ASA-treated patients obtained the adequate response to therapy by compliance improvement. In 80% of patients, which did not respond to KLP therapy in daily dose of 75 mg, the adequate response after the increase to daily dose of 150 mg was observed. The increase of ASA daily dose above 100 mg did not improve in our patients their response to therapy. However, in those patients without a good response to low-dose ASA (< 100 mg daily) the increase to daily dose of 100 mg effectively influenced the aggregatory response.

CONCLUSION

Laboratory monitoring of individual response allows the optimalization of the antiplatelet therapy. The patients who could profit from other type of antiplatelet therapy, such as prasugrel and ticagrelor, can be selected by this method.

Perindoprilat monohydrate

The title compound [systematic name: (1S)-2-((S)-{1-[(2S,3aS,7aS)-2-carboxyoctahydro-1H-indol-1-yl]-1-oxopropan-2-yl}azaniumyl)pentanoate monohydrate], C(17)H(28)N(2)O(5)·H(2)O, (I)·H(2)O, the active metabolite of the antihypertensive and cardiovascular drug perindopril, was obtained during polymorphism screening of perindoprilat. It crystallizes in the chiral orthorhombic space group P2(1)2(1)2(1), the same as the previously reported ethanol disolvate [Pascard, Guilhem, Vincent, Remond, Portevin & Laubie (1991). J. Med. Chem. 34, 663-669] and dimethyl sulfoxide hemisolvate [Bojarska, Maniukiewicz, Sieroń, Fruziński, Kopczacki, Walczyński & Remko (2012). Acta Cryst. C68, o341-o343]. The asymmetric unit of (I)·H(2)O contains one independent perindoprilat zwitterion and one water molecule. These interact via strong hydrogen bonds to give a cyclic R(2)(2)(7) synthon, which provides a rigid molecular conformation. The geometric parameters of all three forms are similar. The conformations of the perhydroindole group are almost identical, but the n-alkyl chain has conformational freedom. A three-dimensional hydrogen-bonding network of O-H···O and N-H···O interactions is observed in the crystal structure of (I)·H(2)O, similar to the other two solvates, but because of the presence of different solvents the three crystal structures have diverse packing motifs. All three solvatomorphs are additionally stabilized by nonclassical weak C-H···O contacts.

Novel pseudopolymorph of the active metabolite of perindopril

The dimethyl sulfoxide hemisolvate of perindoprilat [systematic name: (1S)-2-((S)-{1-[(2S,3aS,7aS)-2-carboxyoctahydro-1H-indol-1-yl]-1-oxopropan-2-yl}azaniumyl)pentanoate dimethyl sulfoxide hemisolvate], C(17)H(28)N(2)O(5)·0.5C(2)H(6)OS, an active metabolite of perindopril, has been synthesized, structurally characterized by single-crystal X-ray diffraction and compared with its ethanol disolvate analogue [Pascard et al. (1991). J. Med. Chem. 34, 663-669]. Both compounds crystallize in the orthorhombic P2(1)2(1)2(1) space group in the same zwitterionic form, with a protonated alanine N atom and an anionic carboxylate group at the n-alkyl chain. The three structural units present in the unit cell (two zwitterions and the solvent molecule) are held together by a rich system of O-H···O, N-H···O and C-H···O hydrogen-bond contacts.

[Markers of endothelial function in the early stages of essential hypertension and the effect of antihypertensive therapy]

OBJECTIVE

Endothelial abnormalities appear to play a role in the pathogenesis of atherosclerotic/atherothrombotic complications of hypertension. They may contribute to the increased risk and severity of target organ damage. The aim of the study was to investigate the endothelial markers in patients at the early stages of mild-to-moderate untreated hypertension with low-to-moderate added risk, and the effect of antihypertensive therapy by perindopril, telmisartan or rilmenidine on endothelial function.

SUBJECTS AND METHODS

The measurements were carried out in 54 previously untreated hypertensive patients before and after one month of antihypertensive therapy by perindopril-arginine (5 mg once daily, n = 20), telmisartan (40 mg once daily, n = 16), rilmenidine (1 mg once daily, n = 18) or after placebo administration (n = 23). A population of 50 healthy normotensive subjects of similar sex, age and ethnic origin was also examined. Plasma thrombomodulin (TM) and von Willebrand factor (vWF) measurements were used as indicators of endothelial dysfunction.

RESULTS

In untreated hypertensive patients compared with a control group of healthy subjects a significant increase of plasma vWF (86.26 +/- 26.18 IU/dl against 69.14 +/- 18.74 IU/dl, P < 0.001) and TM (35.98 +/- 12.98 ng/ml against 29.34 +/- 9.18 ng/ml, P < 0.01) was found. BP was reduced (P < 0.001) or normalized due to each therapy. No significant changes of endothelial markers after placebo administration were found. A decrease of plasma vWF antigen level after 1 month of therapy by perindopril (from 81.93 +/- 22.07 to 72.88 +/- 23.26 IU/dl, P < 0.05) or rilmenidine (from 100.6 +/- 26.09 to 86.07 +/- 27.66 IU/dl, P < 0.05) was observed. No significant changes of vWF antigen levels were found after telmisartan therapy. We failed to find any changes of plasma TM due to any therapy.

CONCLUSION

Our results demonstrate that antihypertensive treatment by perindopril or rilmenidine has a favourable affect on some endothelial markers.

Homocysteine and endothelial markers are increased in patients with chronic liver diseases

BACKGROUND

Hyperhomocysteinaemia is a disorder of methionine metabolism, in which a liver plays a role. It may be frequently due to nutritional deficiencies, particularly low folate status. The aim of the study was to evaluate the serum concentration of homocysteine (Hcy) in patients with chronic liver diseases (CLD), and to assess the relation between Hcy, folate levels, and endothelial markers.

METHODS

Seventy-one patients with CLD and 51 healthy subjects of similar sex and age were investigated. There were 19 patients with steatosis and 52 patients with fibrosis/cirrhosis, classified by the Child-Pugh score as groups A, B and C. Fasting serum Hcy and folate levels were measured by the IMx diagnostic system (ABBOTT, USA). Plasma thrombomodulin (TM) and von Willebrand factor (vWF) as markers of endothelial dysfunction/damage were determined by ELISA methods.

RESULTS

A significant increase of Hcy in all groups of patients with CLD was found: steatosis (P=0.0036), fibrosis/cirrhosis - groups A, B and C (P=0.0067, P<0.0001, P=0.0005, respectively). No significant changes of serum folate in CLD patients were observed, but there was an inverse correlation between Hcy and folate concentrations (r(2)=0.1076, P=0.0003). A significant increase of endothelial markers in CLD patients was found: TM in steatosis (P=0.029), fibrosis/cirrhosis - group A (P=0.0010), groups B and C (P<0.0001, respectively), vWF in fibrosis/cirrhosis - group A (P=0.0003), groups B and C (P<0.0001, respectively). No significant correlation between serum Hcy and endothelial markers was observed.

CONCLUSION

Hyperhomocysteinaemia and abnormalities of endothelial function are demonstrated in CLD patients. The impairment of liver metabolism and local changes in vessel integrity are supposed to play a main role.

The role of renin-angiotensin system in prothrombotic state in essential hypertension

Rheological, haemostatic, endothelial and platelet abnormalities appear to play a role in the thrombotic complications of hypertension. This prothrombotic/hypercoagulable state in hypertension may contribute to the increased risk and severity of target organ damage. It can be induced by the activated renin-angiotensin system (RAS), with abnormalities in endothelial and platelet function, coagulation and fibrinolysis. Treatment of uncomplicated essential hypertension by RAS targeting antihypertensive therapy could result in a reversal of prothrombotic abnormalities, contributing to a reduction of thrombosis-related complications. Since angiotensin converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) have two distinct mechanisms of RAS interruption, it is hypothesized that each therapy might have different impact on the prothrombotic state in hypertensive patients. Some studies demonstrate a beneficial effect of both ACE inhibitors and ARBs on prothrombotic state, in addition to their efficacy to normalize elevated blood pressure. The potentially antithrombotic effect of the RAS inhibiting agents may in turn support the preservation of cardiovascular function. Available data may offer an additional explanation for the efficacy of the RAS targeting agents in the prevention of cardiovascular events in patients with atherosclerotic vascular disease.

Effect of metal ions (Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) and water coordination on the structure and properties of L-arginine and zwitterionic L-arginine

Interactions between metal ions and amino acids are common both in solution and in the gas phase. The effect of metal ions and water on the structure of L-arginine is examined. The effects of metal ions (Li(+), Na(+), K(+), Mg(2+), Ca(2+), Ni(2+), Cu(2+), and Zn(2+)) and water on structures of Arg x M(H2O)m , m = 0, 1 complexes have been determined theoretically by employing the density functional theories (DFT) and using extended basis sets. Of the three stable complexes investigated, the relative stability of the gas-phase complexes computed with DFT methods (with the exception of K(+) systems) suggests metallic complexes of the neutral L-arginine to be the most stable species. The calculations of monohydrated systems show that even one water molecule has a profound effect on the relative stability of individual complexes. Proton dissociation enthalpies and Gibbs energies of arginine in the presence of the metal cations Li(+), Na(+), K(+), Mg(2+), Ca(2+), Ni(2+), Cu(2+), and Zn(2+) were also computed. Its gas-phase acidity considerably increases upon chelation. Of the Lewis acids investigated, the strongest affinity to arginine is exhibited by the Cu(2+) cation. The computed Gibbs energies DeltaG(o) are negative, span a rather broad energy interval (from -150 to -1500 kJ/mol), and are appreciably lowered upon hydration.

Molecular structure and stability of perindopril erbumine and perindopril L-arginine complexes

The methods of theoretical chemistry have been used to elucidate molecular properties of the antihypertensive, cardiovascular protective and antithrombotic perindopril ((2S,3aS,7aS)-1-[(2S)-2-[[(2S)-1-ethoxy-1-oxopentan-2-yl]amino]propanoyl]-2,3,3a,4,5,6,7,7a-octahydroindole-2-carboxylic acid). The geometries and energies of various neutral and ionized complexes of perindopril erbumine and perindopril l-arginine have been computed using HF/6-31G(d) and Becke3LYP/6-31G(d) methods. The calculations showed that in both, the isolated state and water solution perindopril erbumine exists as a neutral complex. In the gas-phase perindopril l-arginine both neutral and ionic complexes are, at the HF level of theory, almost equally stable. The B3LYP level of theory slightly favors single proton transfer complex perindopril l-arginine (by about 14 kJ mol(-1)). In polar solvents like water, the ionized form of perindopril l-arginine becomes much more favored. According to our calculations l-arginine is bound to perindopril more strongly (by about 25 kJ mol(-1)) than erbumine.

Conformational structure of some trimeric and pentameric structural units of heparin

The molecular structure of trimeric units (D-E-F and F-G-H) and the pentamer D-E-F-G-H of heparin (sodium salts and their anionic forms) was studied using the B3LYP/6-31G(d) method. The equilibrium structure of the sodium salts of the trimers and pentamer investigated in the isolated state was determined by multidentate coordination of the sodium cations with oxygen atoms of the sulfate, carboxyl, and hydroxyl (hydroxymethyl) groups, respectively. The displacement of Na+ ions from the binding sites in the sodium salt of oligosaccharides studied resulted in the appreciable change of the overall conformation of the corresponding anion. Upon dissociation, a large change in both the position of the sulfate groups and the conformation across the glycosidic bonds was observed. The stable energy conformations around the glysosidic bonds found for the pentamer investigated are compared and discussed with the available experimental X-ray structural data for the structurally related heparin-derived pentasaccharides in cocrystals with proteins.

Effect of metal ions (Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) and water coordination on the structure of glycine and zwitterionic glycine

Interactions between metal ions and amino acids are common both in solution and in the gas phase. Here, the effect of metal ions and water on the structure of glycine is examined. The effect of metal ions (Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) and water on structures of Gly.Mn+(H2O)m and GlyZwitt.Mn+(H2O)m (m = 0, 2, 5) complexes have been determined theoretically by employing the hybrid B3LYP exchange-correlation functional and using extended basis sets. Selected calculations were carried out also by means of CBS-QB3 model chemistry. The interaction enthalpies, entropies, and Gibbs energies of eight complexes Gly.Mn+ (Mn+ = Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) were determined at the B3LYP density functional level of theory. The computed Gibbs energies DeltaG degrees are negative and span a rather broad energy interval (from -90 to -1100 kJ mol(-1)), meaning that the ions studied form strong complexes. The largest interaction Gibbs energy (-1076 kJ mol(-1)) was computed for the NiGly2+ complex. Calculations of the molecular structure and relative stability of the Gly.Mn+(H2O)m and GlyZwitt.Mn+(H2O)m (Mn+ = Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+; m = 0, 2, and 5) systems indicate that in the complexes with monovalent metal cations the most stable species are the NO coordinated metal cations in non-zwitterionic glycine. Divalent cations Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+ prefer coordination via the OO bifurcated bonds of the zwitterionic glycine. Stepwise addition of two and five water molecules leads to considerable changes in the relative stability of the hydrated species. Addition of two water molecules at the metal ion in both Gly.Mn+ and GlyZwitt.Mn+ complexes reduces the relative stability of metallic complexes of glycine. For Mn+ = Li+ or Na+, the addition of five water molecules does not change the relative order of stability. In the Gly.K+ complex, the solvation shell of water molecules around K+ ion has, because of the larger size of the potassium cation, a different structure with a reduced number of hydrogen-bonded contacts. This results in a net preference (by 10.3 kJ mol(-1)) of the GlyZwitt.K+H2O5 system. Addition of five water molecules to the glycine complexes containing divalent cations Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+ results in a net preference for non-zwitterionic glycine species. The computed relative Gibbs energies are quite high (-10 to -38 kJ mol(-1)), and the NO coordination is preferred in the Gly.Mn+(H2O)5 (Mn+ = Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) complexes over the OO coordination.

Conformational Behavior of Basic Monomeric Building Units of Glycosaminoglycans: Isolated Systems and Solvent Effect

Our work reports in detail the results of systematic large-scale theoretical investigations of the glycosaminoglycan building units 1-OMe DeltaIdoA-2SNa2 (1; 2H1 and 1H2 forms), 1-OMe GlcN-S6SNa2 (2), 1,4-DiOMe GlcNa (3), 1,4-DiOMe GlcN-S3S6SNa3 (4), 1,4-DiOMe IdoA-2SNa2 (5; 4C1, 1C4, and 2So conformations), and 1,4-DiOMe GlcN-S6SNa2 (6) at the BP86/TZ2P level of the density functional theory. The optimized geometries indicate that the most stable structure of these monomeric units in the neutral state is stabilized via "multifurcated" sodium bonds. The equilibrium structure of the biologically active anionic forms of the glycosaminoglycans studied changed considerably in a water solution. The computed interaction energies, DeltaE, of sodium coordinated systems 1-6 are negative and span a rather broad energy interval (from -130 to -590 kcal mol-1). Computations that include the effect of solvation indicated that in water the relative stability of Na+...ligand ionic bonds is considerably diminished. The computed interaction energy in water is small (from -20 to -53 kcal mol-1) and negative, that is, stabilizing.

[Angiotensin converting enzyme inhibitors]

Angiotensin converting enzyme (ACE) is a zinc metallopeptidase which plays a key role in the regulation of important vasoactive peptides through its proteolytic activity. Effective inhibitors of ACE were until recently designed in the absence of the solved 3D structure of this enzyme. About 15 ACE inhibitors are currently commercially available, all of which nonspecifically inhibit both active domains of ACE. Vasopeptidase inhibitors are mixed inhibitors of ACE and neutral endopeptidase (NEP). They contemporarily inhibit the catalytic function of two enzymes and currently are undergoing clinical trials exhibiting better efficacy in the treatment of hypertension and cardiovascular diseases, but in the same time higher risk of adverse side effects compared to ACE inhibitors.