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1.
Phys Chem Chem Phys ; 25(44): 30308-30318, 2023 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-37934509

RESUMO

Acetylcholinesterase (AChE) is an important hydrolase in cholinergic synapses and a candidate target in the treatment of Alzheimer's disease. The lithium treatment widely used in neurological disorders can alter the AChE activity, yet the underlying mechanism of how the ion species regulate the enzymatic activity remains unclear. In this work, we performed combined quantum mechanics/molecular mechanics (QM/MM) and molecular dynamics (MD) simulations and well-tempered metadynamics to understand the modulation of human AChE (hAChE) activity using three alkali metal ions (Li+, Na+, and K+) in different concentrations. Our simulations show that the binding affinity and catalytic activity are affected by different ion species through allosteric ion coordination geometries on the hAChE complex and distant electrostatic screening effect. A Li+ cluster involving D330, E393, and D397 residues and three Li+ ions was found to be highly conserved and can be critical to the enzyme activity. Binding energy calculations indicate that the electrostatic screening from allosterically bound cations can affect the key residues at the catalytic site and active-site gorge, including E199. Furthermore, an increase in ion concentration can lead to lower reactivity, especially for Li+ ions, which exhibit more cation-hAChE contacts than Na+ and K+. The selective ion binding and their preferred modulation on hAChE are highly related to ion species. This work provides a molecular perspective on selective modulation by different ion species of the enzyme catalytic processes.


Assuntos
Acetilcolinesterase , Metais Alcalinos , Humanos , Acetilcolinesterase/química , Metais Alcalinos/química , Lítio/química , Sódio/química , Cátions
2.
Bioorg Chem ; 141: 106914, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37857065

RESUMO

Bioactive phenolic compounds are commonly found in medications, with examples including apomorphine, estrone, thymol, estradiol, propofol, o-phenylphenol, l-Dopa, doxorubicin, tetrahydrocannabinol (THC), and cannabidiol (CBD). This study is the first to explore the creation and assessment of metal and ammonium phenolate salts using CBD as an example. CBD is used in medicine to treat anxiety, insomnia, chronic pain, and inflammation, but its bioavailability is limited due to poor water solubility. In this study exploit a synthetic route to convert CBD into anionic CBD-salts to enhance water solubility. Various CBD-salts with metal and ammonium counterions such as lithium (Li+), sodium (Na+), potassium (K+), choline hydroxide ([(CH3)3NCH2CH2OH]+), and tetrabutylammonium ([N(C4H9)4]+) have been synthesized and characterized. These salts are obtained in high yields, ranging from 74 % to 88 %, through a straightforward dehydration reaction between CBD and alkali metal hydroxides (LiOH, NaOH, KOH) or ammonium hydroxides (choline hydroxide, tetrabutylammonium hydroxide). These reactions are conducted in either ethanol, methanol, or a methanol:water mixture, maintaining a 1:1 molar ratio between the reactants. Comprehensive characterization using Fourier-Transform Infrared Spectroscopy (FT-IR), Nuclear Magnetic Resonance (NMR) spectroscopy, and elemental (CHN) analysis confirms the formation of CBD-salts, as evidenced by the absence of aromatic hydroxyl resonances or stretching frequencies. The molecular formulas of CBD salts were determined based on CHN analysis, and CBD quantification from acid regeneration experiments. Characterization data confirms that each CBD phenolate in a specific CBD salt was electrostatically stabilized by one of the either alkali metal or ammonium ion. The CBD-salts are highly susceptible to acidic conditions, readily reverting back to the original CBD. The percentage and purity of CBD in the CBD-metal/ammonium salts have been studied using High-Performance Liquid Chromatography (HPLC) analysis. Solubility studies indicate that the conversion of CBD into CBD salts significantly enhances its solubility in water, ranging from 110 to 1606 folds greater than pure CBD. Furthermore, the pharmacokinetic evaluation of oral administration of CBD-salts compared to CBD were determined in rats.


Assuntos
Compostos de Amônio , Canabidiol , Metais Alcalinos , Ratos , Animais , Canabidiol/química , Canabidiol/farmacocinética , Sais/química , Espectroscopia de Infravermelho com Transformada de Fourier , Metanol , Metais Alcalinos/química , Preparações Farmacêuticas , Sódio/química , Fenóis , Colina , Hidróxidos , Água
3.
Int J Mol Sci ; 24(20)2023 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-37895065

RESUMO

Nucleoside radicals are key intermediates in the process of DNA damage, and alkali metal ions are a common group of ions in living organisms. However, so far, there has been a significant lack of research on the structural effects of alkali metal ions on nucleoside free radicals. In this study, we report a new method for generating metalized nucleoside radical cations in the gas phase. The radical cations [Ade+M-H]•+ (M = Li, Na) are generated by the 280 nm ultraviolet photodissociation (UVPD) of the precursor ions of lithiated and sodiated ions of 2-iodoadenine in a Fourier transform ion cyclotron resonance (FT ICR) cell. Further infrared multiphoton dissociation (IRMPD) spectra of both radical cations were recorded in the region of 2750-3750 cm-1. By combining these results with theoretical calculations, the most stable isomers of both radicals can be identified, which share the common characteristics of triple coordination patterns of the metal ions. For both radical species, the lowest-energy isomers undergo hydrogen transfer. Although the sugar ring in the most stable isomer of [Ade+Li-H]•+ is in a (South, syn) conformation similar to that of [Ado+Na]+, [Ade+Na-H]•+ is distinguished by the unexpected opening of the sugar ring. Their theoretical spectra are in good agreement with experimental spectra. However, due to the flexibility of the structures and the complexity of their potential energy surfaces, the hydrogen transfer pathways still need to be further studied. Considering that the free radicals formed directly after C-I cleavage have some similar spectral characteristics, the existence of these corresponding isomers cannot be ruled out. The findings imply that the structures of nucleoside radicals may be significantly influenced by the attached alkali metal ions. More detailed experiments and theoretical calculations are still crucial.


Assuntos
Adenosina , Metais Alcalinos , Nucleosídeos , Metais Alcalinos/química , Lítio/química , Sódio/química , Cátions/química , Hidrogênio , Modelos Teóricos , Açúcares , Radicais Livres , Análise Espectral
4.
J Oleo Sci ; 72(9): 831-837, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37648460

RESUMO

Alkali series with different atomic numbers affect the physicochemical properties of aqueous solutions. The micellar properties of aqueous solutions of dodecanoate as surfactants were measured by changing the counterions (C12-Na, C12-K, C12-Rb, and C12-Cs). A plot of Krafft temperature vs. alkali metal atomic number showed a downward convex curve, with its minimum temperature (20°C) in the C12-K system. By contrast, a plot of the critical micelle concentration (CMC) vs. alkali metal atomic number exhibited an upward convex curve with the maximum CMC (25.6 mmol L-1) at C12-K. Furthermore, the minimum surface tension (γ min ) of the solution at the CMC increased with increasing atomic number (C12-Na ≈ C12-K < C12-Rb < C12-Cs). The size of the dodecanoate micelles decreased with increasing atomic number. The ionization degree of the micelles also increased with increasing atomic number of the alkali metal. Small-angle X-ray scattering (SAXS) measurements revealed that alkali dodecanoate micelles formed spherical to ellipsoidal structures. In addition, micelles from the shell region showed large electrostatic repulsion, judging from the shape of the spectrum in the higher Q -1 region. From the measurement results of the solubilization of naphthalene into the micelles, the size of the micelles corresponded to the maximum solubilization quantity of naphthalene.


Assuntos
Ácidos Láuricos , Micelas , Ácidos Láuricos/química , Metais Alcalinos/química , Propriedades de Superfície , Cátions/química , Solubilidade
5.
J Oleo Sci ; 72(5): 543-548, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37121679

RESUMO

The selectivity of adsorption between alkali metal ions (Li+, Na+, K+, Rb+, and Cs+) based on the ionic functional groups of the surfactants was studied using two types of surfactants, dodecanoic acid (DA) and sodium dodecyl sulfate (SDS), in the foam separation system. The results showed that Li+ was preferably removed by foam separation using DA. The removal rates of other alkali metal ions were relatively low, and there were no significant differences among other alkali metal ions (Na+, K+, Rb+, and Cs+). However, Cs+ exhibited the highest removal rate among the mixed alkali metals by foam separation using SDS. From these results, the selectivity of the alkali metal in foam separation was dependent on the type of surfactant.


Assuntos
Metais Alcalinos , Metais Alcalinos/química , Metais Alcalinos/isolamento & purificação , Ácidos Láuricos/química , Dodecilsulfato de Sódio/química
6.
J Mol Model ; 29(5): 147, 2023 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-37069404

RESUMO

CONTEXT: Nanomaterials enjoy a great surface-to-surface area ratio, small size, extremely high stability, satisfactory bio-compatibility, improved permeability, specificity in receptor targeting, and tunable lifetime. This paper investigates alkali metal-doped borospherenes M@C4B32 (in which M denotes K, Na, and Li) as a highly efficient alternative for the delivery of drugs using density functional theory (DFT) calculations. A borospherene with a B36 nanocage doped with four C atoms (i.e., C4B32) recently showed promising performance. Therefore, the present work investigates C4B32 nanoclusters doped with alkali metals for the effective delivery of drugs. METHODS: This paper primarily seeks to evaluate the interaction between thioguanine (TG) as a cancer drug and pristine M@C4B32 through DFT (PBE/6-31 + G (d)) calculations. The UV-Vis spectroscopy indicated a redshift in the complex electronic spectra to higher wavelengths (i.e., lower energy levels). Hence, K@C4B32 was concluded to be effective in TG delivery.


Assuntos
Metais Alcalinos , Teoria Quântica , Metais Alcalinos/química , Lítio , Sódio , Íons/química
7.
Int J Mol Sci ; 24(4)2023 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-36834487

RESUMO

This article investigated the structure, and the spectroscopic and antimicrobial properties of mandelic acid and its alkali metal salts. The electron charge distribution and aromaticity in the analyzed molecules were investigated using molecular spectroscopy methods (FT-IR, FT-Raman, 1H NMR, and 13C NMR) and theoretical calculations (structure, NBO, HOMO, LUMO, energy descriptors, and theoretical IR and NMR spectra). The B3LYP/6-311++G(d,p) method was used in the calculations. The antimicrobial activities of mandelic acid and its salt were tested against six bacteria: Gram-positive Listeria monocytogenes ATCC 13932, Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, and Loigolactobacillus backii KKP 3566; Gram-negative Escherichia coli ATCC 25922 and Salmonella Typhimurium ATCC 14028, as well as two yeast species, Rhodotorulla mucilaginosa KKP 3560 and Candida albicans ATCC 10231.


Assuntos
Anti-Infecciosos , Metais Alcalinos , Sais/química , Espectroscopia de Infravermelho com Transformada de Fourier , Elétrons , Metais Alcalinos/química , Anti-Infecciosos/química , Análise Espectral Raman
8.
Dalton Trans ; 52(4): 947-954, 2023 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-36597695

RESUMO

The reactions between SnCl2 and three equivalents of the alkali metal phosphido-borane complexes [R2P(BH3)]M yield the corresponding tris(phosphido-borane)stannate complexes [LnM{R2P(BH3)}3Sn] [R2 = iPr2, LnM = (THF)3Li (2Li), (Et2O)Na (2Na), (Et2O)K (2K); R2 = Ph2, LnM = (THF)Li (3Li), (THF)(Et2O)Na (3Na), (THF)(Et2O)K (3K); R2 = iPrPh, LnM = (THF)4Li (4Li)]. In each case X-ray crystallography reveals an anion consisting of a trigonal pyramidal tin centre coordinated by the P atoms of the phosphido-borane ligands. These tris(phosphido-borane)stannate anions coordinate to the alkali metal cations via their BH3 hydrogen atoms in a variety of modes to give monomers, dimers, and polymers, depending on the alkali metal and the substituents at the phosphorus centres. In contrast, reactions between SnCl2 and three equivalents of [tBu2P(BH3)]M (M = Li, Na) gave the known hydride [M{tBu2P(BH3)}2SnH], according to multinuclear NMR spectroscopy.


Assuntos
Boranos , Complexos de Coordenação , Metais Alcalinos , Boranos/química , Compostos de Estanho , Complexos de Coordenação/química , Ânions , Metais Alcalinos/química , Lítio
9.
Dalton Trans ; 52(4): 962-970, 2023 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-36597846

RESUMO

Heterobimetallic tert-butoxides of alkali metal cations with tetravalent actinide centers exhibit two distinctive structural motifs, [AnM2(OtBu)6] and [AnM3(OtBu)7] (AnIV = Th, U and MI = Li, Na, K, Rb, Cs), evidently governed by the size of the alkali metal ions. Both [AnM3(OtBu)7] AnM3 (AnIV = U, MI = Li; AnIV = Th, MI = Li, Na) and [AnM2(OtBu)6] AnM2 (AnIV = U, MI = Na-Cs; AnIV = Th, MI = K-Cs) compounds are obtained in nearly quantitative yields by reacting actinide and alkali metal silyl amides with an excess of tert-butyl alcohol. The AnM3 complexes form a cubane-type coordination motif, whereas the AnM2 complexes display a geometry resembling two face-shared bipyramids. The sodium derivatives of thorium and uranium (ThNa3 and UNa2) allow the determination of the structural transition threshold as a function of the ratio of the ionic radii ri(AnIV)/ri(MI). The AnM3 complexes are formed for ratios above 0.92 and the AnM2 type is formed for ratios below 0.87. All compounds are unambiguously characterized in both solution and solid states by NMR and IR spectroscopic studies and single crystal X-ray diffraction analyses, respectively.


Assuntos
Metais Alcalinos , Urânio , Metais Alcalinos/química , Sódio/química , Lítio/química , Cátions , Urânio/química
10.
J Biomol Struct Dyn ; 41(19): 9997-10008, 2023 11.
Artigo em Inglês | MEDLINE | ID: mdl-36458452

RESUMO

G-rich sequences are intrinsic parts of the genome, widespread in promoters, telomeres, or other regulatory regions. The in vivo existence and biological significance have established the functional aspect of G-quadruplex structures and thus have developed immense interest in exploring their therapeutic aspects. Herein, using biophysical methods, we examined the structural status and comprehensive cation-dependence of a 17-bp G-rich genomic sequence (SKGT17) located in the coding region of the human TRPA1 gene, known to be associated with various neurovascular, cardiovascular, and respiratory conditions. TRPA1 is primarily seen as a therapeutic target for the development of novel analgesics. Bioinformatics analysis has suggested that 17-bp quadruplex motif is a binding site for transcription factor 'Sp1'. The formation and recognition of SKGT17 G-quadruplex might impact its regulatory functioning. Biophysical studies confirmed that the presence of alkali metal ions facilitated the formation of G-quadruplex in parallel topology. Native gel further substantiated the formation of a biomolecular species. Circular dichroism (CD), UV-thermal melting (Tm), and CD melting confirmed the formation of parallel G-quadruplex with metal ion-dependent stability. The stability of the G-quadruplex formed is found to be significantly high in the presence of K+ ions than that of other ions. Intriguingly, we have also established that this segment of the TRAP1 gene favors G-quadruplex formation over its participation in the corresponding duplex formation under K+ ions conditions. This study attempts to explain the rationale for the stabilization of G-quadruplex in the presence of alkali metal ions and may add to a better understanding and insights into DNA-metal ions interactions.


Assuntos
Quadruplex G , Metais Alcalinos , Humanos , DNA/química , Cátions , Metais Alcalinos/química , Regiões Promotoras Genéticas/genética , Dicroísmo Circular , Canal de Cátion TRPA1/genética , Proteínas de Choque Térmico HSP90
11.
Talanta ; 254: 124201, 2023 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-36549141

RESUMO

Tetracyclines (TCs) are a family of broad-spectrum antibiotics. During the manufacturing process or storage, epimerization of tetracyclines could occur, leading to 4-epimers which are nearly inactive. From an analytical point of view, isomers are often difficult to distinguish. Previously, four pairs of TCs (oxytetracycline, tetracycline, doxycycline, chlortetracycline and their respective 4-epimers) were differentiated by mass spectrometry (MS) through protonated ions. However, they do not follow common rules and so it is still quite difficult to differentiate between them. In order to solve this, the four pairs were differentiated in the current study by collision induced dissociation (CID) spectra of the alkali adduct ions, including lithium, sodium and potassium. In the spectra of the sodium adducts, all studied tetracyclines showed a tendency to form [M+Na-NH3]+ ions, while the 4-epimers liked to form [M+Na-NH3-H2O]+ ions. Meanwhile, energy resolved mass spectrometry (ERMS) showed that all four 4-epimers' sodium adducts had the tendency to fragment at higher energy points. In the CID spectra of lithium adducts of TCs, a similar trend was observed for three pairs, except for doxycycline. For potassium adducts, the fragmentation was found to be less discriminative. As was derived from the 3D model, the four pairs all interact with the alkali metal through the dimethyl amino group at the C-4 position. The lithium adduct species also bound through the hydroxyl group at the C-5 position. If the TCs did not have a hydroxyl group at the C-5 position, they bound with the hydroxyl group at the C-6 position. For the same TC, with an increase of the diameter of the metal ion, the loss of H2O decreased gradually. As sodium adduct ions are common during the ionization process, TCs and their 4-epimers could be differentiated rapidly by ERMS of the sodium adduct ions.


Assuntos
Lítio , Metais Alcalinos , Espectrometria de Massas por Ionização por Electrospray/métodos , Tetraciclinas/química , Doxiciclina , Metais Alcalinos/química , Íons/química , Sódio/química , Antibacterianos , Potássio
12.
Inorg Chem ; 61(49): 19838-19846, 2022 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-36503245

RESUMO

We report the oxidative addition of phenylsilane to the complete series of alkali metal (AM) aluminyls [AM{Al(NONDipp)}]2 (AM = Li, Na, K, Rb, and Cs). Crystalline products (1-AM) have been isolated as ether or THF adducts, [AM(L)n][Al(NONDipp)(H)(SiH2Ph)] (AM = Li, Na, K, Rb, L = Et2O, n = 1; AM = Cs, L = THF, n = 2). Further to this series, the novel rubidium rubidiate, [{Rb(THF)4}2(Rb{Al(NONDipp)(H)(SiH2Ph)}2)]+ [Rb{Al(NONDipp)(H)(SiH2Ph)}2]-, was isolated during an attempted recrystallization of Rb[Al(NONDipp)(H)(SiH2Ph)] from a hexane/THF mixture. Structural and spectroscopic characterizations of the series 1-AM confirm the presence of µ-hydrides that bridge the aluminum and alkali metals (AM), with multiple stabilizing AM···π(arene) interactions to either the Dipp- or Ph-substituents. These products form a complete series of soluble, alkali metal (hydrido) aluminates that present a platform for further reactivity studies.


Assuntos
Metais Alcalinos , Metais Alcalinos/química , Sódio/química , Lítio , Rubídio/química , Íons
13.
J Chem Phys ; 157(17): 174301, 2022 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-36347691

RESUMO

Using infrared predissociation spectroscopy of cryogenic ions, we revisit the vibrational spectra of alkali metal ion (Li+, Na+, K+) di- and triglycine complexes. We assign their most stable conformation, which involves metal ion coordination to all C=O groups and an internal NH⋯NH2 hydrogen bond in the peptide backbone. An analysis of the spectral shifts of the OH and C=O stretching vibrations across the different metal ions and peptide chain lengths shows that these are largely caused by the electric field of the metal ion, which varies in strength as a function of the square of the distance. The metal ion-peptide interaction also remotely modulates the strength of internal hydrogen bonding in the peptide backbone via the weakening of the amide C=O bond, resulting in a decrease in internal hydrogen bond strength from Li+ > Na+ > K+.


Assuntos
Hidrogênio , Metais Alcalinos , Ligação de Hidrogênio , Vibração , Metais Alcalinos/química , Íons/química , Metais/química , Sódio/química , Ácido Nitrilotriacético , Peptídeos/química
14.
Phys Chem Chem Phys ; 24(37): 22950-22959, 2022 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-36125205

RESUMO

The gas-phase structures of cationized glycine (Gly), including complexes with Li+, Na+, K+, Rb+, and Cs+, are examined using infrared multiple-photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser, in conjunction with ab initio calculations. To identify the structures present in the experimental studies, measured IRMPD spectra are compared to spectra calculated at B3LYP/6-311+G(d,p) for the Li+, Na+, and K+ complexes and at B3LYP/def2TZVP for the Rb+ and Cs+ complexes. Single-point energy calculations were carried out at the B3LYP, B3P86, and MP2(full) levels using the 6-311+G(2d,2p) basis set for Li+, Na+, K+ and the def2TZVPP basis set for Rb+ and Cs+. The Li+ and Na+ complexes are identified as metal cation coordination to the amino nitrogen and carbonyl oxygen, [N,CO]-tt, although Na+(Gly) may have contributions from additional structures. The heavier metal cations coordinate to either the carbonyl oxygen, [CO]-cc, or the carbonyl oxygen and hydroxy oxygen, [CO,OH]-cc, with the former apparently preferred for Rb+ and Cs+ and the latter for K+. These two structures reside in a double-well potential and different levels of theory predict very different relative stabilities. Some experimental evidence is provided that MP2(full) theory provides the most accurate relative energies.


Assuntos
Glicina , Metais Alcalinos , Cátions/química , Glicina/química , Metais Alcalinos/química , Conformação Molecular , Oxigênio
15.
Phys Chem Chem Phys ; 24(35): 20803-20812, 2022 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-36000593

RESUMO

K+ channels allow selective permeation of K+, but not physiologically abundant Na+, at almost diffusion limit rates. The conduction mechanism of K+ channels is still controversial, with experimental and computation studies supporting two distinct conduction mechanisms: either with or without water inside the channel. Here, we employ a bottom-up approach on hydrated alkali metal complexes of a model peptide of K+ channels, Ac-Tyr-NHMe, to characterize metal-peptide, metal-water, and water-peptide interactions that govern the selectivity of K+ channels at a molecular level. Both the extension to the series of alkali metal ions and to temperature-dependent studies (approaching physiological values) have revealed the clear difference between permeable and non-permeable ions in the spectral features of the ion complexes. Furthermore, the impact of hydration is discussed in relation to the K+ channels by comparisons of the non-hydrated and hydrated complexes.


Assuntos
Complexos de Coordenação , Metais Alcalinos , Álcalis , Íons/química , Lasers , Metais Alcalinos/química , Peptídeos , Análise Espectral , Água/química
16.
Molecules ; 27(10)2022 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-35630527

RESUMO

It was established that isopropyl salicylate can be used similarly to 1,3-diketones as a key component for a new efficient extraction system for selective separation of alkali metal cations. According to DFT modeling of complexes of isopropyl salicylate and 1,3-diketone with alkali metal cations (Li+, Na+, K+), six-membered metallacycles are formed whose stability decreases along the series Li > Na > K, which results in the observed enhanced affinity to lithium. The extraction ability of isopropyl salicylate is manifested in the presence of trioctylphosphine oxide (TOPO). The newly obtained complexes of isopropyl salicylate with alkali metal cations as well as their extracts in a mixture with TOPO are characterized by means of FT-IR, Raman, and NMR spectroscopy. The probable structure of the extracted lithium complex is presumed and the role of TOPO in the extraction process is investigated in detail. Extraction experiments showed extremely high separation coefficients for Li/Na and Li/K pairs in the extraction from a model multi-component solution.


Assuntos
Lítio , Metais Alcalinos , Cátions , Lítio/química , Metais Alcalinos/química , Compostos Organofosforados , Salicilatos , Sódio/química , Espectroscopia de Infravermelho com Transformada de Fourier
17.
J Am Soc Mass Spectrom ; 33(8): 1427-1442, 2022 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-35535863

RESUMO

Noncovalent interactions between alkali metals and amino acids are critical for many biological processes, especially for proper function of protein ion channels; however, many precise binding affinities between alkali metals and amino acids still need to be measured. This study addresses this need by using threshold collision-induced dissociation with a guided ion beam tandem mass spectrometer to measure binding affinities between potassium cations and the aliphatic amino acids: Gly, Ala, hAla, Val, Leu, and Ile. These measurements are supplemented by theoretical calculations and include commentary on effects of enthalpy, entropy, and structural preference. Notably, all levels of theory indicate that the lowest-lying isomers at 298 K have K+ binding to the carbonyl oxygen in either a monodentate ([CO]) or bidentate ([CO,OH]) fashion, isomers that are linked in a double-well potential. This complicates the analysis of the data, although does not greatly influence the final results. Analysis of the resulting cross sections includes accounting for multiple ion-molecule collisions, internal energy of reactant ions, and unimolecular decay rates. The resulting experimental bond dissociation energies generally increase as the polarizability of the amino acid increases, results that agree well with quantum chemical calculations done at the B3LYP, B3P86, and MP2(full) levels of theory, with B3LYP-GD3BJ predicting systematically larger values.


Assuntos
Ácidos Graxos , Metais Alcalinos , Aminoácidos , Cátions/química , Entropia , Metais Alcalinos/química , Potássio/química , Termodinâmica
18.
Chemistry ; 28(18): e202104260, 2022 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-35170823

RESUMO

Arylmethyl anions allow alkali-metals to bind in a σ-fashion to the lateral carbanionic centre or a π-fashion to the aryl ring or in between these extremities, with the trend towards π bonding increasing on descending group 1. Here we review known alkali metal structures of diphenylmethane, fluorene, 2-benzylpyridine and 4-benzylpyridine. Next, we synthesise Li, Na, K monomers of these diarylmethyls using polydentate donors PMDETA or Me6 TREN to remove competing oligomerizing interactions, studying the effect that two aromatic rings has on negative charge (de)localisation via NMR, X-ray crystallographic and DFT studies. Diphenylmethyl and fluorenyl anions maintain C(H)-M interactions regardless of alkali-metal, although the adjacent arene carbons engage in interactions with larger alkali-metals. Introducing a nitrogen atom into the ring (at the 2- or 4-position) encourages relocalisation of negative charge away from the deprotonated carbon and onto nitrogen. Phenyl(2-pyridyl)methyl moves from an enamide formation at one extremity (lithium) to an aza-allyl formation at the other extremity (potassium), while C- or N-coordination modes become energetically viable for Na and K phenyl(4-pyridyl)methyl complexes.


Assuntos
Metais Alcalinos , Álcalis , Ânions/química , Cátions/química , Metais Alcalinos/química , Modelos Moleculares
19.
Angew Chem Int Ed Engl ; 61(1): e202113662, 2022 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-34750941

RESUMO

Prussian Blue (PB), which was first discovered as robust blue-colored pigment in the year 1706, has shown promising prospects in disease treatment, energy conversion, water splitting, and sensing. Relying on the uniform 3.2 Å-sized pore channels as well as high stability in aqueous environments, in this study, we pioneered in situ preparation of polycrystalline PB membranes to justify their dye rejection and metal ion discrimination ability in aqueous environments. Among various factors, the introduction of calcined NiFe layered double hydroxide buffer layers on porous α-Al2 O3 substrates was found to play a paramount role in the formation of continuous polycrystalline PB membranes, thereby leading to excellent dye rejection efficiency (>99.0 %). Moreover, prepared PB membranes enabled discriminating different monovalent metal ions (e.g., Li+ , Na+ , and K+ ) depending on their discrepancy in Stokes diameters, showing great promise for lithium extraction from smaller-sized metal ions.


Assuntos
Ferrocianetos/química , Hidróxidos/química , Eletrólitos , Metais Alcalinos/química , Tamanho da Partícula
20.
Dalton Trans ; 50(47): 17438-17454, 2021 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-34766180

RESUMO

With the steady development of metal-organic framework (MOF) materials, this peculiar class of three-dimensional materials has found application prospects in a myriad of areas. The integration of different metals with various categories of ligands engendered a full gamut of frameworks, which of course are supplemented by diversified modification methods. Amongst many metal centers utilized to design and synthesize targeted MOFs, alkali/alkaline earth metal-based MOFs are gaining significant attention because these metal centers can be regarded as human endogenous metals. Numerous studies have shown that alkali/alkaline earth metal MOFs (A/A-E MOFs) tend to have better properties than other metals. This is because A/A-E MOFs offer better biocompatibility, so it is expected to be used in a broader field of biomedicine in the near future. This review mainly introduces the application of A/A-E MOF materials in drug delivery, sensing, and some materials with unique biomedical applications, and elaborates the challenges, obstacles and development of some A/A-E MOF materials in the biomedical field.


Assuntos
Materiais Biocompatíveis/química , Pesquisa Biomédica , Estruturas Metalorgânicas/química , Metais Alcalinos/química , Metais Alcalinoterrosos/química , Sistemas de Liberação de Medicamentos , Humanos
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