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1.
Sci Rep ; 11(1): 511, 2021 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-33436908

RESUMO

Dengue is an arboviral infection with high rates of morbidity and mortality throughout the tropics and sub-tropics. This work studied the status of pentraxin (CRP/SAP) protein, ferritin, TNF-α and IL-1ß levels in Dengue patients of different pathophysiological manifestations. Accordingly, clinically confirmed Dengue cases (n = 97) were enrolled and subsequently blood parameters were studied by Haematology cell counter and Biochemistry Autoanalyser. CRP, SAP, ferritin, TNF-α and IL-1ß ELISA were done in all the samples by using standard ELISA kits. Statistical Analysis was done in all the experiments. The levels of CRP (p < 0.0001), SAP (p < 0.0001), ferritin (p < 0.0001), TNF-α (p < 0.0001) and IL-1ß (p < 0.0001) were high in patients with Severe Dengue as compared to Dengue without warning signs. High levels of SGOT, SGPT and decreased platelet counts were found in severe patients as compared to Healthy donor. CRP/SAP as well as TNF-α/IL-1ß were independently associated with both dengue severity and overall disease manifestation. Statistically significant increased CRP, SAP, ferritin, TNF-α and IL-1ß titres were correlated in patients with severe clinical manifestations as compared to mild disease forms of dengue. Elevated levels of pentraxin, TNF-α/IL-1ß in blood during dengue infection could act as an early predictor in Severe Dengue infection.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32528904

RESUMO

Background: Post Kala Azar Dermal Leishmaniasis (PKDL) is a non-fatal dermal sequel of Visceral Leishmaniasis (VL), affecting individuals worldwide. Available diagnostic tools lack sensitivity and specificity toward identifying macular (MAC) PKDL patients, due to low parasite load in patients' sample. Confirmatory test like punch biopsy are invasive and painful. Considering the rural nature of this disease and the prevailing situation of diagnostic scenario, PKDL patients mostly remains unattended from receiving proper medical care. They in turn act as "mobile parasite reservoir," responsible for VL transmission among healthy individuals (HI). This study aims to identify PKDL disease specific glycated protein biomarkers, utilizing the powerful LC-MS/MS technology, which is the tool of choice to efficiently identify and quantify disease specific protein biomarkers. These identified PKDL disease specific novel glycoproteins could be developed in future as immunochromatographic based assay for efficient case detection. Methodology: Previously our lab had identified importance of glycated (Circulating Immune Complexes) CICs, among PKDL patients. This study aims to further characterize disease specific glycated protein biomarkers, among MAC PKDL patients for both diagnostic and prognostic evaluation of the disease. LC-MS/MS based comparative spectral count analysis of MAC PKDL to polymorphic (POLY) PKDL, HI, and Cured (CR) individuals were performed. Proteins level alterations among all study groups were confirmed by Western blot and enzyme-linked immunosorbant Assay (ELISA). Results: Among MAC PKDL patients 43, 60, 90 proteins were altered compared to POLY PKDL, HI, and CR groups, respectively. Filtering for the most significant proteins, Plasminogen (PLG) and Vitronectin (VTN) were identified which promisingly identified MAC PKDL cases. Active surveillance results from endemic districts of West Bengal revealed drastic rise of MAC PKDL cases, alarming the urgency for field adaptive efficient biomarker. Conclusion: This current study aims to establish PLG and VTN as novel diagnostic and prognostic protein biomarker for MAC and POLY PKDL cases management.

3.
Anal Bioanal Chem ; 412(7): 1573-1583, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31932862

RESUMO

We report a smartphone-paper-based sensor impregnated with cetyltrimethylammonium bromide modified silver nanoparticles (AgNPs/CTAB) for determination of Fe3+ in water and blood plasma samples. The methodology for determination of Fe3+ is based on the change in signal intensity of AgNPs/CTAB fabricated on a paper substrate after the deposition of analyte, using a smartphone followed by processing with ImageJ software. The mechanism of sensing for detection and determination of Fe3+ is based on the discoloration of AgNPs which impregnated the paper substrate. The discoloration is attributed to the electron transfer reaction taking place on the surface of NPs in the presence of CTAB. Fe3+ was determined when the paper was impregnated with 1 mM AgNPs for 5 min of reaction time and the substrate was kept under acidic conditions. The linear range for determination of total iron in terms of Fe3+ was 50-900 µg L-1 with a limit of determination (LOD) of 20 µg L-1 and coefficient of variation (CV) of 3.2%. The good relative recovery of 91.3-95.0% and interference studies showed the selectivity of the method for determination of total iron in water and blood plasma samples. Smartphone-paper-based sensors have advantages of simplicity, rapidity, user-friendliness, low cost, and miniaturization of the method for on-site determination of total iron compared to methods that require sophisticated analytical instruments. Graphical abstract Smartphone-paper-based sensor with cetyltrimethylammonium bromide modified silver nanoparticles for determination of Fe3+ in water and blood plasma samples.


Assuntos
Ferro/análise , Ferro/sangue , Papel , Smartphone , Água/química , Limite de Detecção
4.
Dalton Trans ; 48(32): 12336-12348, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31347648

RESUMO

A novel flexible "N", "O"-rich hydrazide-based Schiff base chemoreceptor, 2-(benzamido)-N'-((pyridin-2-yl)methylene)benzohydrazide (L), was designed, synthesised and characterised via1H-NMR, IR spectroscopy, ESI-MS spectrometry and single-crystal XRD analysis. The receptor showed a colorimetric and fluorometric "turn on" response in the presence of only Ni2+ ions in methanol-Tris-HCl buffer medium (10 mM, pH 7.2, 1 : 1 v/v). The Job plot analysis revealed that the receptor forms a 2 : 1 complex with Ni2+ ions, which was further confirmed via the ESI-MS analysis. A single crystal of the L-Ni2+ complex (2) was also isolated. The detection limit was calculated to be 1.8 µM colorimetrically and 1.18 µM fluorometrically, which are much lower than those recommended as per the WHO guidelines for drinking water. The experimental results were further supported by DFT studies. The chemosensor L was applied for the recovery of contaminated water samples, building of molecular logic gate, smart phone-based analysis and live cell imaging.

5.
J Med Virol ; 91(10): 1873-1876, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31243775

RESUMO

Dengue is the most common arboviral infection globally, but its pathogenesis is poorly explored. Vascular endothelial growth factor (VEGF) has an essential role in the host defense against viral infection. However, not much information is available regarding its status in dengue patients from the eastern zone of India. In the present investigation, the level of VEGF was investigated for its possible utility as a dengue severity marker. Accordingly, confirmed dengue cases were enrolled during 2016-2018. Serum from all the study subjects was subjected to the standard enzyme-linked immunosorbent assay test for VEGF analysis. In addition, we assessed the association of VEGF to dengue severity. The study revealed that VEGF titers (P < .0001) were significantly increased in severe dengue (SD) patients in contrast to those with a milder form of dengue. An association was obtained between VEGF and increased SGOT (r = 0.517 with P < .0001) while VEGF had a negative correlation with platelets in SD patients (r = -0.331 with P = .001). Enhanced VEGF titers along with decreased platelets had a good association with SD. The investigation revealed that high VEGF titers are novel indicators of dengue severity. However, our results must be verified in a study evaluating a larger number of dengue patients.


Assuntos
Dengue/sangue , Dengue/metabolismo , Fator A de Crescimento do Endotélio Vascular/sangue , Estudos de Casos e Controles , Dengue/epidemiologia , Feminino , Humanos , Índia/epidemiologia , Masculino , Fator A de Crescimento do Endotélio Vascular/metabolismo
6.
Photochem Photobiol Sci ; 18(6): 1512-1525, 2019 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-30977507

RESUMO

In this paper, a novel flexible Schiff base chemosensor N'-(2-hydroxy-3-methoxybenzylidene)-2-(benzamido)benzohydrazide (L) has been designed, synthesised and characterised by 1H-NMR, IR spectroscopy, ESI-MS spectrometry and single crystal XRD analysis. A significant fluorescence enhancement of L was observed only in the presence of Ni2+ ions with a detection limit of 3.64 µM whereas Cu2+ induced fluorescence quenching, although both the metals showed colorimetric responses in methanol-Tris-HCl buffer (10 mM, pH 7.2) solution (1 : 1, v/v). The single crystal structure of L-Cu2+ has also been determined. No major interference by the other effective background cations (Fe3+, Fe2+, Co2+, Zn2+, Cd2+, Hg2+, Pb2+, Cr3+, Ag+, Al3+ and Mn2+) was observed even at a higher concentration of analytes. The experimental results were further supported by DFT studies. The chemosensor L can be applied to the formation of binary logical devices, recovery of contaminated water samples and living intracellular media.

7.
Acta Trop ; 190: 73-79, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30395811

RESUMO

Dengue fever is an acute viral infection transmitted by arthropods but may evolve to severe clinical manifestations. Descriptions of the role of circulating immune modulators such as cytokines or chemokines in dengue immunopathogenesis have largely relied on data from South-east Asia and America, while India is poorly represented. This study characterizes dengue cases from West Bengal, eastern India, with respect to clinical profile and pro-inflammatory and inflammatory cytokines. We evaluated the profile of both inflammatory and anti-inflammatory cytokines (IFNγ, IL6, IL10, IL12 and TGFß) and chemokines (IL8, CXCL9, CXCL10 and RANTES) in 100 hospitalized NS1/IgM confirmed Dengue patients during the epidemic in West Bengal during 2017. Additionally, all necessary blood investigations of the study subjects were performed. The patients mostly hailed from Kolkata, followed by Nadia, 24 Parganas (North and South), Murshidabad and Midnapore. The most common presentations apart from fever and bodyache were gastrointestinal symptoms. An elevated levels of cytokines IL6 and IL10 chemokine IL8 and CXCL10 along with decreased RANTES were found in the patients with Severe Dengue as compared to mild forms of dengue (p < 0.0001) during 3-6 days of infections. A significant association was obtained between most of cytokine and increased SGPT, haematocrit, albumin and decreased platelet count, whereas a negative correlation with the level of RANTES to haematocrit (r=-0.220 with p = 0.029) was found in severe dengue cases with altered liver function parameters. This is the first study demonstrating cytokine and chemokine association with dengue severity from the eastern part of India. Taken together, this study demonstrated that the altered expression levels of IL6, IL10, IL8, CXCL10 and RANTES had significant associations with dengue severity parameters.


Assuntos
Quimiocinas/sangue , Citocinas/sangue , Dengue/imunologia , Quimiocina CCL5 , Feminino , Humanos , Masculino , Dengue Grave/imunologia
8.
Dalton Trans ; 45(28): 11540-53, 2016 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-27353454

RESUMO

A novel, quinoline-based smart probe L has been designed for the detection of Al(3+) and Cu(2+) at physiological range. The unprecedented solvent-dependent sensitivities of the probe L for simultaneous detection of Al(3+) and Cu(2+) ions with high selectivity and sensitivity have been observed for the first time. It displays quick responses through visible colorimetric as well as fluorogenic changes towards both Al(3+) and Cu(2+), as delineated by absorption and fluorescence titrations. The sensitivity of the fluorescence-based assay (12.6 nM) for Al(3+) and (18.4 nM) for Cu(2+) is far below the limit recommended in the World Health Organization (WHO) guidelines for drinking water. From (1)H NMR data, the Job plot and the ESI-MS spectrum, 1 : 2 stoichiometric complexations between L and both metals have been established. The geometry and spectral property of L and its metal complexes have been well rationalized by DFT calculations. This probe L has been tested as being highly suitable for mapping Al(3+) and Cu(2+) in human breast cancer cells, MCF7, thus providing a wonderful candidate for tracking Al(3+) and Cu(2+) in biological organisms and processes. The proposed chemosensor L has also been successfully applied for analysis of real samples.


Assuntos
Alumínio/análise , Colorimetria/métodos , Cobre/análise , Corantes Fluorescentes/química , Solventes/química , Água/química , Soluções
9.
Indian J Exp Biol ; 53(11): 719-25, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26669014

RESUMO

Dengue, a serious viral infection caused by the mosquito vector, Aedes aegyptii, affects about 390 million people annually from more than 125 countries across the globe. However, until now, there is no reliable clinical or laboratory indicator to accurately predict the development of dengue severity. Here, we explored critical pathophysiological determinants like IL8, circulating immune complex (CIC) and cryoglobulin in dengue-infected patients for identification of novel dengue severity biomarker(s). Totally, 100 clinically suspected dengue cases were tested by NS1 ELISA and MAC ELISA for dengue virus aetiology. For control, 49 healthy volunteers were included. Blood profiling (complete hemogram and liver function test) of patient population were done using automated cell counter and standard auto analyzer based biochemical analysis. Serum CIC was quantified by PEG precipitation. Serum cryoglobulins were estimated by Folin assay. Levels of serum IL-8 were assessed by standard sandwich ELISA kits. Patient CIC were further characterized by SDS Gel electrophoresis. Forty per cent of the cases tested positive, of which 11 patients had severe clinical manifestation. The mean ±SEM of cryoglobulin concentration for DHF, DF, and HC were 1.30 ± 0.31, 0.59 ± 0.08 and 0.143 ± 0.009 µg/µl, respectively. Thus, DHF and DF patients have shown 9- and 2.2-fold increase in cryoglobulin levels; and 18- and 5-fold increased CIC, respectively compared to HC patients. The mean ±SEM of CIC-PEG index for DHF, DF and HC were 491 ± 41.22, 146 ± 14.19 and 27.98 ± 2.56, respectively. Raised levels of IL8 titers were also found in all 11 DHF patients. Peak levels of CIC, cryoglobulin and IL8 titers were associated with thrombocytopenia. SDS PAGE analysis of CIC from DHF revealed the presence of at least six protein bands that were not observed in samples from DF and HC. Prediction efficacy of IL8, CIC and cryoglobulin for DHF was determined using the receiver operator characteristic curve (ROC). The area under the curve was 1.00 for IL8, 0.99 for CIC and 0.74 for cryoglobulins. Overall, the results suggest that CIC, IL-8 and cryoglobulins may serve as important laboratory parameters to monitor dengue infection progression.


Assuntos
Complexo Antígeno-Anticorpo/sangue , Crioglobulinas/metabolismo , Dengue/sangue , Interleucina-8/sangue , Feminino , Humanos , Masculino
10.
Dalton Trans ; 44(29): 13261-71, 2015 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-26126410

RESUMO

A reversible fluorescent-colorimetric imino-pyridyl bis-Schiff base receptor (N(1)E,N(4)E)-N(1),N(4)-bis(pyridine-4-ylmethylene)benzene-1,4-diamine for the detection of both Al(3+) and HSO3(-) in aqueous medium has been developed. Receptor exhibits an excellent selective fluorescent-colorimetric response toward Al(3+). The sensitivity of the fluorescent based assay (0.903 µM) for Al(3+) is far below the limit recommended in the World Health Organization (WHO) guidelines for drinking water (7.41 µM). From (1)H NMR data, the Job plot and the ESI-MS spectrum, 1 : 2 stoichiometric complexation between and Al(3+) has been established. Receptor shows remarkable detection ability in a wide pH range of 4-11 and was successfully utilised in the determination of Al(3+) in aqueous solution of bovine serum albumin protein, and of HSO3(-) in real food samples. Moreover, shows a highly selective colorimetric response to HSO3(-) by changing its colour from yellow to colorless immediately without any interference from other anions.


Assuntos
Alumínio/análise , Corantes Fluorescentes/química , Fenilenodiaminas/química , Bases de Schiff/química , Sulfitos/análise , Água/análise , Animais , Cátions/análise , Bovinos , Colorimetria/métodos , Análise de Alimentos/métodos , Limite de Detecção , Modelos Moleculares , Piridinas/química , Soroalbumina Bovina/química , Espectrometria de Fluorescência/métodos
11.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 10): m1389, 2011 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-22058699

RESUMO

In the title coordination polymer, [Cu(2)I(2)(C(14)H(14)N(4))(C(18)H(15)P)(2)](n), the Cu(I) atom is coordinated by two I atoms, one P atom and one N atom in a fairly regular tetra-hedral arrangement. A crystallographic inversion centre generates a Cu(2)I(2) diamond with a Cu-Cu separation of 3.0120 (5) Å. The complete N,N'-(1-pyridin-4-yl-ethethyl-idene)-hydrazine mol-ecule is also generated by inversion symmetry, and this bridging ligand leads to [011] polymeric chains in the crystal structure.

12.
Dalton Trans ; (40): 8755-64, 2009 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-19809751

RESUMO

Four side-off compartmental ligands L1-L4 [L1 = N,N'-ethylenebis(3-formyl-5-methyl-salicylaldimine), L2 = N,N'-1-methylethylenebis(3-formyl-5-methylsalicylaldimine), L3 = N,N'-1,1-dimethylethylenebis(3-formyl-5-methylsalicylaldimine) and L4= N,N'-cyclohexenebis(3-formyl-5-methylsalicylaldimine)] having two binding sites, N2O2 and O4, have been chosen to synthesize mononuclear and dinuclear manganese(III) complexes with the aim to study their catecholase activity using 3,5-di-tert-butylcatechol (3,5-DTBC) as substrate in the presence of molecular oxygen. In all cases only mononuclear manganese complexes (1-4) were obtained, with manganese coordination taking place at the N2O2 binding site only, irrespective of the amount of manganese salt used. All these complexes have been characterized by routine physico-chemical techniques. Complex MnL2Cl.4H2O (2) has further been structurally characterized by X-ray single crystal structure analysis. Four dinuclear manganese complexes, 5-8, were obtained after condensing the two pending formyl groups on each ligand (L1-L4) with aniline followed by reaction with MnCl2 to put the second Mn atom onto another N2O2 site. The catalytic activity of all complexes 1-8 has been investigated following the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) with molecular oxygen in two different solvents, methanol and acetonitrile. The study reveals that the catalytic activity is influenced by the solvent and to a significant extent by the backbone of the diamine and the behavior seems to be related mainly to steric rather than electronic factors. Experimental data suggest that a correlation, the lower the E(1/2) value the higher the catalytic activity, can be drawn between E(1/2) and Vmax of the complexes in a particular solvent. The EPR measurements suggest that the catalytic property of the complexes is related to the metal center(s) participation rather than to a radical mechanism.


Assuntos
Manganês/química , Compostos Organometálicos/química , Compostos Organometálicos/síntese química , Catecol Oxidase/química , Catecol Oxidase/metabolismo , Cristalografia por Raios X , Espectroscopia de Ressonância de Spin Eletrônica , Ligantes , Modelos Moleculares , Estrutura Molecular
13.
Inorg Chem ; 48(15): 7430-45, 2009 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-19572498

RESUMO

The reaction of cis-[Fe(III)(cyclam)Cl(2)]Cl with 1 equiv of sodium N-diethyldithiocarbamate, toluene-3,4-dithiolate, and maleonitriledithiolate in methanol in the presence of triethylamine afforded the cations [Fe(III)(cyclam)(Et(2)dtc)](2+) (1), [Fe(III)(cyclam)(tdt)](+) (2), and [Fe(III)(cyclam)(mnt)](+) (3), which were isolated as triflate, hexafluorophosphate, and tetrafluoroborate salt, respectively, using sodium triflate, potassium hexafluorophosphate, or sodium tetrafluoroborate as the source for the counteranion. Complexes 1, 2, and 3 possess an S = (1)/(2) ground state (low-spin ferric d(5)). These salts were characterized by X-ray crystallography, UV-vis, Mössbauer, and electron paramagnetic resonance spectroscopies. Cyclic voltammetry revealed that 2 and 3 are reversibly one-electron-reduced, generating neutral 2(red) and 3(red), respectively, and one-electron-oxidized, generating dicationic 2(ox) and 3(ox), respectively. Fe and S K-edge X-ray absorption spectroscopy (XAS) revealed that 2 (S = (1)/(2)) and 2(ox) (S = 0) possess a low-spin ferric ion. Complexes 2 and 3 are S,S'-coordinated to a closed-shell dithiolate(2-) ligand, whereas 2(ox) and 3(ox) consist of a low-spin ferric ion antiferromagnetically coupled to a dithiolate(1-) pi radical ligand. They are singlet diradicals [Fe(III)(cyclam)(dithiolate(*))](2+). The analysis of the sulfur K pre-edge transitions reveals significant multiplet effects in the spectra of 2 and 2(ox), which provide rare experimental evidence for a singlet diradical description for 2(ox). Mössbauer spectroscopy on frozen solutions of 2(red) clearly show the presence of a high-spin ferrous ion (S = 2). The experimentally established electronic structures of the three members of the electron transfer series [Fe(cyclam)(dithiolate)](2+,+,0) have been verified by broken symmetry density functional theoretical calculations, which have been calibrated against the experiment by calculating XAS and Mössbauer spectra.


Assuntos
Ferro/química , Lactamas Macrocíclicas/química , Compostos Organometálicos/química , Compostos de Sulfidrila/química , Ânions/química , Cristalografia por Raios X , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres/química , Ligantes , Modelos Moleculares , Estrutura Molecular , Espectrofotometria , Espectroscopia de Mossbauer
14.
Acta Crystallogr Sect E Struct Rep Online ; 65(Pt 8): o1728, 2009 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-21583445

RESUMO

The complete molecule of the title compound, C(20)H(26)N(4), is generated by a crystallographic centre of inversion and the central eight-carbon chain adopts a fully extended conformation. In the crystal, the molecules pack in layers parallel to (010).

15.
Acta Crystallogr Sect E Struct Rep Online ; 65(Pt 8): o1745, 2009 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-21583456

RESUMO

THE TITLE COMPOUND (SYSTEMATIC NAME: 1,1',2,2'-tetra-phenyl-2,2'-azinodiethanone), C(28)H(20)N(2)O(2), was obtained by the reaction of benzil monohydrazone with chromium(III) nitrate. The dibenzyl-idene hydrazine unit is nearly planar (r.m.s. deviation = 0.073 Å) and the two benzoyl units are oriented almost perpendicular to it [dihedral angle = 87.81 (2), 87.81 (2)°]. The mol-ecules are linked into chains along the c axis by C-H⋯O hydrogen bonds and the chains are cross-linked via C-H⋯π inter-actions involving the benzoyl phenyl rings.

16.
Acta Crystallogr Sect E Struct Rep Online ; 65(Pt 8): o1810, 2009 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-21583513

RESUMO

In the title compound, C(26)H(19)N(3)O, the dimethyl-ene hydrazine (-C=N-N=C-) unit is approximately planar, the torsion angle around the N-N bond being 162.2 (6)°. The phenyl and benzoyl-phenyl rings at one end of the hydrazine unit are aligned at angles of 9.5 (5) and 88.5 (4)°, respectively, with respect to the hydrazine unit, whereas the benzene ring at the other end is twisted by an angle of 14.4 (4)°. In the crystal structure, mol-ecules are linked into centrosymmetric dimers by inter-molecular C-H⋯O hydrogen bonds. The monoclinic crystal under investigation shows pseudo-merohedral twinning with twin fractions of 0.63 and 0.37.

17.
Inorg Chem ; 45(24): 9798-811, 2006 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-17112277

RESUMO

Substitution of natural nucleobases in PNA oligomers with ligands is a strategy for directing metal ion incorporation to specific locations within a PNA duplex. In this study, we have synthesized PNA oligomers that contain up to three adjacent bipyridine ligands and examined the interaction with Ni2+ and Cu2+ of these oligomers and of duplexes formed from them. Variable-temperature UV spectroscopy showed that duplexes containing one terminal pair of bipyridine ligands are more stable upon metal binding than their nonmodified counterparts. While binding of one metal ion to duplexes that contain two adjacent bipyridine pairs makes the duplexes more stable, additional metal ions lower the duplex stability, with electrostatic repulsions being, most likely, an important contributor to the destabilization. UV titrations showed that the presence of several bipyridine ligands in close proximity of each other in PNA oligomers exerts a chelate effect. A supramolecular chelate effect occurs when several bipyridines are brought next to each other by hybridization of PNA duplexes. EPR spectroscopy studies indicate that even when two Cu2+ ions coordinate to a PNA duplex in which two bipyridine pairs are next to each other, the two metal-ligand complexes that form in the duplex are far enough from each other that the dipolar coupling is very weak. EXAFS and XANES show that the Ni2+-bipyridine bond lengths are typical for [Ni(bipy)2]2+ and [Ni(bipy)3]2+ complexes.


Assuntos
2,2'-Dipiridil/química , Metais/metabolismo , Ácidos Nucleicos Peptídicos/química , Ácidos Nucleicos Peptídicos/metabolismo , Pareamento de Bases , Sítios de Ligação , Cobalto/química , Cobalto/metabolismo , Cobre/química , Cobre/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Ligantes , Metais/química , Níquel/química , Níquel/metabolismo , Titulometria , Raios Ultravioleta
18.
J Am Chem Soc ; 127(42): 14628-39, 2005 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-16231915

RESUMO

Recent studies on metal incorporation in ligand-modified nucleic acids have focused on the effect of metal coordination on the stability of metal-containing duplexes or triplexes and on the metal binding selectivity but did not address the effect of the sequence of the nucleic acid in which the ligands are incorporated. We have introduced 8-hydroxyquinoline Q in 10-mer PNA strands with various sequences and have investigated the properties of the duplexes formed from these strands upon binding of Cu(2+). Variable-temperature UV-vis spectroscopy shows that, in the presence of Cu(2+), duplexes are formed even from ligand-modified Q-PNA strands that have a large number of mismatches. Spectrophotometric titrations demonstrate that at any temperature, one Cu(2+) ion binds a pair of Q-PNA strands that each contain one 8-hydroxyquinoline, but below the melting temperature, the PNA duplex exerts a supramolecular chelate effect, which prevents the transformation in the presence of excess Cu(2+) of the 1:2 Cu(2+):Q-PNA complexes into 1:1 complexes. EPR spectroscopy gives further support for the existence in the duplexes of [CuQ(2)] moieties that are similar to the corresponding square planar synthetic complex formed between Cu(2+) and 8-hydroxyquinoline. As PNA duplexes show a preferred handedness due to the chiral induction effect of a C-terminal l-lysine, which is transmitted through stacking interactions within the duplex, only if the metal-containing duplex has complementary strands, does it show a chiral excess measured by CD spectroscopy. The strong effect of the metal-ligand moiety is suggestive of an increased correlation length in PNA duplexes that contain such moieties. These results indicate that strong metal-ligand alternative base pairs significantly diminish the importance of Watson-Crick base pairing for the formation of a stable PNA duplex and lead to high mismatch tolerance, a principle that can be used in the construction of hybrid inorganic-nucleic acid nanostructures.


Assuntos
Cobre/química , Oxiquinolina/química , Ácidos Nucleicos Peptídicos/química , Ligantes , Estrutura Molecular , Ácidos Nucleicos Peptídicos/síntese química , Espectrofotometria Ultravioleta , Temperatura
19.
Chem Commun (Camb) ; (13): 1420-1, 2002 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-12125583

RESUMO

Targeted synthesis of new supramolecular motifs of metalloporphyrins in crystals by a concerted mechanism of molecular recognition in three dimensions, aided by organic ligands, is presented; it involves induced assembly of [tetrakis(4-hydroxyphenyl)porphyrinato]zinc species by a combination of axial coordination through bridging bipyridyls and of lateral hydrogen bonding.


Assuntos
2,2'-Dipiridil/farmacologia , Metaloporfirinas/química , Zinco/química , Engenharia Química , Cristalização , Cristalografia por Raios X , Ligação de Hidrogênio , Metaloporfirinas/metabolismo , Conformação Molecular , Estrutura Molecular
20.
Acta Crystallogr C ; 58(Pt 6): m344-6, 2002 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-12050418

RESUMO

The title compound, [5,10,15,20-meso-tetrakis(4-hydroxyphenyl)porphyrinato-kappa(4)N]zinc(II) tris(dibenzo-24-crown-8) methanol tetrasolvate, [Zn(C(44)H(28)N(4)O(4))].3C(24)H(32)O(8).4CH(4)O, was synthesized and its molecular structure precisely characterized by low-temperature single-crystal analysis. All the components are involved in hydrogen bonding with each other, thus forming an extensively hydrogen-bonded supramolecular lattice. The functionalized porphyrin moiety coordinates both equatorially and axially to the neighboring species.

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