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1.
Inorg Chem ; 62(36): 14546-14558, 2023 Sep 11.
Artículo en Inglés | MEDLINE | ID: mdl-37647164

RESUMEN

Complexes generated in the gas phase involving the purine nucleobase guanine bound to second and third generation platinum drugs, namely, carboplatin (CarboPt) and oxaliplatin (OxaliPt), were investigated by combining tandem mass spectrometry, collision-induced dissociation (CID), infrared multiple photon dissociation spectroscopy (IRMPD), and density functional theory (DFT) calculations. As the first step, a spectroscopic characterization of the protonated platinum drugs was accomplished. Protonation of both CarboPt and OxaliPt in the gas phase occurs on one of the two carbonyl groups of the cyclobutanedicarboxylate and oxalate ligand, respectively. Such protonation has been postulated by several theoretical studies as a key preliminary step in the hydrolysis of Pt drugs under acidic conditions. Subsequently, the protonated drugs react with guanine in solution to generate a complex of general formula [Pt drug + H + guanine]+, which was then mass-selected. CID experiments provided evidence of the presence of strong binding between guanine and platinum-based drugs within the complexes. The structures of the two complexes have also been examined by comparing the experimental IRMPD spectra recorded in two spectral regions with DFT-computed IR spectra. For each system, the IRMPD spectra agree with the vibrational spectra calculated for the global minimum structures, which present a monodentate complexation of Pt at the N7 position of canonical guanine. This binding scheme is therefore akin to that observed for cisplatin, while other coordination sites yield substantially less stable species. Interestingly, in the case of oxaliplatin, the IRMPD spectra are consistent with the presence of two isomeric forms very close in energy.


Asunto(s)
Guanina , Espectrometría de Masas en Tándem , Carboplatino , Oxaliplatino , Espectrofotometría Infrarroja , Platino (Metal)
2.
J Inorg Biochem ; 247: 112342, 2023 10.
Artículo en Inglés | MEDLINE | ID: mdl-37536163

RESUMEN

The inorganic antineoplastic drug cisplatin was made to react in solution with the dipeptide cysteinylglycine (CysGly), chosen as a functional model of glutathione, and the reaction products were analyzed using electrospray ionization mass spectrometry (ESI-MS). Selected complexes, i.e., the primary substitution product cis-[PtCl(NH3)2(CysGly)]+ and the chelate cis-[PtCl(NH3)(CysGly)]+, were submitted to IR multiple photon dissociation (IRMPD) spectroscopy obtaining their vibrational features. The experimental IR ion spectra were compared with the calculated IR absorptions of different plausible isomeric families, finding CysGly to bind preferentially platinum(II) via its deprotonated thiolic group in the monovalent complex, cis-[PtCl(NH3)2(CysGly)]+, and to evolve in the S,N-bound chelate structure cis-[PtCl(NH3)(CysGly)]+ through the SH and NH2 functionality of the cysteine residue. Moreover, our findings indicate that the platination reaction does not affect the CysGly peptide bond, which remains in its trans configuration. These results provide additional insights into the reactivity of Pt(II)-complexes with glutathione which is involved in cellular cisplatin resistance.


Asunto(s)
Antineoplásicos , Cisplatino , Humanos , Cisplatino/química , Antineoplásicos/química , Espectrofotometría Infrarroja , Dipéptidos , Glutatión
3.
J Agric Food Chem ; 71(9): 4005-4015, 2023 Mar 08.
Artículo en Inglés | MEDLINE | ID: mdl-36849438

RESUMEN

Naringenin (Nar) and its structural isomer, naringenin chalcone (ChNar), are two natural phytophenols with beneficial health effects belonging to the flavonoids family. A direct discrimination and structural characterization of the protonated forms of Nar and ChNar, delivered into the gas phase by electrospray ionization (ESI), was performed by mass spectrometry-based methods. In this study, we exploit a combination of electrospray ionization coupled to (high-resolution) mass spectrometry (HR-MS), collision-induced dissociation (CID) measurements, IR multiple-photon dissociation (IRMPD) action spectroscopy, density functional theory (DFT) calculations, and ion mobility-mass spectrometry (IMS). While IMS and variable collision-energy CID experiments hardly differentiate the two isomers, IRMPD spectroscopy appears to be an efficient method to distinguish naringenin from its related chalcone. In particular, the spectral range between 1400 and 1700 cm-1 is highly specific in discriminating between the two protonated isomers. Selected vibrational signatures in the IRMPD spectra have allowed us to identify the nature of the metabolite present in methanolic extracts of commercial tomatoes and grapefruits. Furthermore, comparisons between experimental IRMPD and calculated IR spectra have clarified the geometries adopted by the two protonated isomers, allowing a conformational analysis of the probed species.


Asunto(s)
Chalconas , Espectrometría de Movilidad Iónica , Espectrofotometría Infrarroja
4.
J Inorg Biochem ; 237: 112017, 2022 12.
Artículo en Inglés | MEDLINE | ID: mdl-36209532

RESUMEN

The reactivity of a widely used metal based antineoplastic drug, cisplatin, cis-PtCl2(NH3)2, with L-cysteine (Cys) has been investigated using a combination of electrospray ionization mass spectrometry (ESI-MS), IRMPD gas phase ion spectroscopy and DFT calculations. The cysteine lateral chain represents one of the main platination sites in proteins, which is believed to be related to the resistance mechanisms to cisplatin. The vibrational features of the mass-selected substitution product cis-[PtCl(NH3)2(Cys)]+ and the intercepted cis-[PtCl(NH3)2(H2O)(Cys)]+ intermediate complex were compared to calculated IR spectra, enabling the assessment of the sampled ions structures. In cis-[PtCl(NH3)2(Cys)]+, cysteine was found to bind platinum through the sulfur atom as a thiolate zwitterion, highlighting the enhanced acidity of the cysteine thiol group upon metal coordination. The cis-[PtCl(NH3)2(H2O)(Cys)]+ structure complies with the non-covalent encounter complex, formed by cis-[PtCl(NH3)2(H2O)]+ and neutral cysteine. This species is able to undergo the substitution process to produce cis-[PtCl(NH3)2(Cys)]+ when activated as a mass-isolated ion suggesting its participation in the reaction mechanism of cisplatin with cysteine in solution. Finally, the DFT-calculated energy profile for the substitution reaction was correlated with the peculiar gas-phase reactivity of this non-covalent complex, resulting to be 10-fold less reactive toward substitution than the corresponding methionine complex.


Asunto(s)
Antineoplásicos , Cisplatino , Cisplatino/química , Platino (Metal) , Cisteína/química , Aminoácidos , Teoría Funcional de la Densidad , Antineoplásicos/química , Análisis Espectral , Iones
5.
ACS Omega ; 7(23): 19535-19544, 2022 Jun 14.
Artículo en Inglés | MEDLINE | ID: mdl-35721943

RESUMEN

Genistein is a naturally occurring polyphenol belonging to the family of flavonoids with estrogenic properties and proven antioxidant, anti-inflammatory, and hormonal effects. Genistein and its derivatives are involved in radical scavenging activity by way of mechanisms based on sequential proton-loss electron transfer. In view of this role, a detailed structural characterization of its bare deprotonated form, [geni-H]-, generated by electrospray ionization, has been performed by tandem mass spectrometry and infrared multiple photon dissociation (IRMPD) spectroscopy in the 800-1800 cm-1 spectral range. Quantum chemical calculations at the B3LYP/6-311+G(d,p) level of theory were carried out to determine geometries, thermochemical data, and anharmonic vibrational properties of low-lying isomers, enabling to interpret the experimental spectrum. Evidence is gathered that the conjugate base of genistein exists as a single isomeric form, which is deprotonated at the most acidic site (7-OH) and benefits from a strong intramolecular H-bond interaction between 5-OH and the adjacent carbonyl oxygen in the most stable arrangement.

6.
Molecules ; 27(10)2022 May 14.
Artículo en Inglés | MEDLINE | ID: mdl-35630621

RESUMEN

The sulfonamide-zinc ion interaction, performing a key role in various biological contexts, is the focus of the present study, with the aim of elucidating ligation motifs in zinc complexes of sulfa drugs, namely sulfadiazine (SDZ) and sulfathiazole (STZ), in a perturbation-free environment. To this end, an approach is exploited based on mass spectrometry coupled with infrared multiple photon dissociation (IRMPD) spectroscopy backed by quantum chemical calculations. IR spectra of Zn(H2O+SDZ-H)+ and Zn(H2O+STZ-H)+ ions are consistent with a three-coordinate zinc complex, where ZnOH+ binds to the uncharged sulfonamide via N(heterocycle) and O(sulfonyl) donor atoms. Alternative prototropic isomers Zn(OH2)(SDZ-H)+ and Zn(OH2)(STZ-H)+ lie 63 and 26 kJ mol-1 higher in free energy, respectively, relative to the ground state Zn(OH)(SDZ)+ and Zn(OH)(STZ)+ species and do not contribute to any significant extent in the sampled population.


Asunto(s)
Sulfonamidas , Zinc , Iones , Espectrofotometría Infrarroja , Sulfanilamida , Zinc/química
8.
Chemistry ; 28(33): e202200300, 2022 Jun 10.
Artículo en Inglés | MEDLINE | ID: mdl-35412692

RESUMEN

The structure of an isolated Ag+ (benzylamine) complex is investigated by infrared multiple photon dissociation (IRMPD) spectroscopy complemented with quantum chemical calculations of candidate geometries and their vibrational spectra, aiming to ascertain the role of competing cation-N and cation-π interactions potentially offered by the polyfunctional ligand. The IRMPD spectrum has been recorded in the 800-1800 cm-1 fingerprint range using the IR free electron laser beamline coupled with an FT-ICR mass spectrometer at the Centre Laser Infrarouge d'Orsay (CLIO). The resulting IRMPD pattern points toward a chelate coordination (N-Ag+ -π) involving both the amino nitrogen atom and the aromatic π-system of the phenyl ring. The gas-phase reactivity of Ag+ (benzylamine) with a neutral molecular ligand (L) possessing either an amino/aza functionality or an aryl group confirms N- and π-binding affinity and suggests an augmented silver coordination in the product adduct ion Ag + ( benzylamine ) ( L ) .


Asunto(s)
Bencilaminas , Plata , Cationes/química , Ligandos , Plata/química , Espectrofotometría Infrarroja/métodos
9.
Anal Chem ; 93(44): 14869-14877, 2021 11 09.
Artículo en Inglés | MEDLINE | ID: mdl-34714056

RESUMEN

Thyroid hormones are biologically active small molecules responsible for growth and development regulation, basal metabolic rate, and lipid and carbohydrate metabolism. Liquid chromatography mass spectrometry (LC-MS) can be used to quantify thyroid hormones blood level with high speed and selectivity, aiming to improve the diagnosis and treatment of the severe pathological conditions in which they are implicated, i.e., hypo- and hyperthyroidism. In this work, the gas-phase behavior of the isomeric thyroid hormones triiodothyronine (T3) and reverse triiodothyronine (rT3) in their deprotonated form was studied at a molecular level using MS-based techniques. Previously reported collision-induced dissociation experiments yielded distinct spectra despite the high structural similarity of the two compounds, suggesting different charge sites to be responsible. Infrared multiple photon dissociation spectroscopy on [T3-H]- and [rT3-H]- was performed, and the results were interpreted using DFT and MP2 calculations, assessing the prevalence of T3 in the carboxylate form and rT3 as a phenolate isomer. The different deprotonation sites of the two isomers were also found to drive their ion-mobility behavior. In fact, [T3-H]- and [rT3-H]- were successfully separated. Drift times were correlated with collisional cross section values of 209 and 215 Å2 for [T3-H]- and [rT3-H]-, respectively. Calculations suggested the charge site to be the main parameter involved in the different mobilities of the two anions. Finally, bare [T3-H]- and [rT3-H]- were made to react with neutral acetylacetone and trifluoroacetic acid, confirming rT3 to be more acidic than T3 in agreement with the calculated gas-phase acidities of T3 and rT3 equal to 1345 and 1326 kJ mol-1, respectively.


Asunto(s)
Triyodotironina Inversa , Triyodotironina , Cromatografía Liquida , Hormonas Tiroideas , Tiroxina
10.
J Am Soc Mass Spectrom ; 32(8): 2206-2217, 2021 Aug 04.
Artículo en Inglés | MEDLINE | ID: mdl-34236851

RESUMEN

Methionine (Met) plays an important role in the metabolism of cisplatin anticancer drug. Yet, methionine platination in aqueous solution presents a highly complex pattern of interconnected paths and intermediates. This study reports on the reaction of methionine with the active aqua form of cisplatin, cis-[PtCl(NH3)2(H2O)]+, isolating the encounter complex of the reactant pair, {cis-[PtCl(NH3)2(H2O)]+·Met}, by electrospray ionization. In the unsolvated state, charged intermediates are characterized for their structure and photofragmentation behavior by IR ion spectroscopy combined with quantum-chemical calculations, obtaining an outline of the cisplatin-methionine reaction at a molecular level. To summarize the major findings: (i) the {cis-[PtCl(NH3)2(H2O)]+·Met} encounter complex, lying on the reaction coordinate of the Eigen-Wilkins preassociation mechanism for ligand substitution, is delivered in the gas phase and characterized by IR ion spectroscopy; (ii) upon vibrational excitation, ligand exchange occurs within {cis-[PtCl(NH3)2(H2O)]+·Met}, releasing water and cis-[PtCl(NH3)2(Met)]+, along the calculated energy profile; (iii) activated cis-[PtCl(NH3)2(Met)]+ ions undergo NH3 departure, forming a chelate complex, [PtCl(NH3)(Met)]+, whose structure is congruent with overwhelming S-Met ligation as the primary coordination step. The latter process involving ammonia loss marks a difference with the prevailing chloride replacement in protic solvent, pointing to the effect of a low-polarity environment.


Asunto(s)
Antineoplásicos/química , Cisplatino/química , Metionina/química , Espectrometría de Masa por Ionización de Electrospray/métodos , Espectrofotometría Infrarroja/métodos , Amoníaco/química , Quelantes/química , Ligandos , Modelos Químicos , Modelos Moleculares , Conformación Molecular , Platino (Metal)/química , Soluciones , Solventes/química
11.
Int J Mol Sci ; 22(2)2021 Jan 12.
Artículo en Inglés | MEDLINE | ID: mdl-33445631

RESUMEN

Pantothenic acid, also called vitamin B5, is an essential nutrient involved in several metabolic pathways. It shows a characteristic preference for interacting with Ca(II) ions, which are abundant in the extracellular media and act as secondary mediators in the activation of numerous biological functions. The bare deprotonated form of pantothenic acid, [panto-H]-, its complex with Ca(II) ion, [Ca(panto-H)]+, and singly charged micro-hydrated calcium pantothenate [Ca(panto-H)(H2O)]+ adduct have been obtained in the gas phase by electrospray ionization and assayed by mass spectrometry and IR multiple photon dissociation spectroscopy in the fingerprint spectral range. Quantum chemical calculations at the B3LYP(-D3) and MP2 levels of theory were performed to simulate geometries, thermochemical data, and linear absorption spectra of low-lying isomers, allowing us to assign the experimental absorptions to particular structural motifs. Pantothenate was found to exist in the gas phase as a single isomeric form showing deprotonation on the carboxylic moiety. On the contrary, free and monohydrated calcium complexes of deprotonated pantothenic acid both present at least two isomers participating in the gas-phase population, sharing the deprotonation of pantothenate on the carboxylic group and either a fourfold or fivefold coordination with calcium, thus justifying the strong affinity of pantothenate for the metal.


Asunto(s)
Calcio/química , Ácido Pantoténico/química , Gases/química , Fotones , Teoría Cuántica , Espectrofotometría Infrarroja
12.
J Am Soc Mass Spectrom ; 32(3): 736-743, 2021 Mar 03.
Artículo en Inglés | MEDLINE | ID: mdl-33499589

RESUMEN

The discrimination of d-galactosamine (G), representative of the amino-sugar class of compounds, has been probed through nano-ESI-FT-ICR mass spectrometry by isolating the relevant [C·H·G]+ proton-bound complexes with the enantiomers of the cyclochiral resorcin[4]arene C and allowing them to react toward three primary amines (B = EtNH2, iPrNH2, and (R)- and (S)-sBuNH2). The system under investigation presents several features that help to unveil the behavior of unprotected G in such a supramolecular architecture: (i) the hydrophobic derivatization of the C convex side forces the polar guest G to be coordinated by the cyclochiral concave region; (ii) protonated d-galactosamine exists as an anomeric mixture, dynamically interconverting throughout the experimental time-window; and (iii) different basicities of B allow the experiment to subtly tune the reactivity of the [C·H·G]+ complexes. Three [C·H·G]+ aggregate-types were found to exist, differing in both their origin and reactivity. The most reactive adducts ([C·H·G]ESI+), generated in the electrospray environment, undergo a G-to-B ligand exchange in competition with a partial isomerization to the unreactive [C·H·G]GAS+-type complexes. Finally, the poorly reactive [C·H·G]SOL+ aggregates are formed in solution over an hours-long time scale. A cyclochirality effect on the reactivity was found to depend on the considered [C·H·G]+ aggregate-type.

13.
Chemistry ; 27(7): 2348-2360, 2021 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-33175428

RESUMEN

The structures of proton-bound complexes of 5,7-dimethoxy-4H-chromen-4-one (1) and basic amino acids (AAs), namely, histidine (His) and lysine (Lys), have been examined by means of mass spectrometry coupled with IR ion spectroscopy and quantum chemical calculations. This selection of systems is based on the fact that 1 represents a portion of glabrescione B, a natural small molecule of promising antitumor activity, while His and Lys are protein residues lining the cavity of the alleged receptor binding site. These species are thus a model of the bioactive adduct, although clearly the isolated state of the present study bears little resemblance to the complex biological environment. A common feature of [1+AA+H]+ complexes is the presence of a protonated AA bound to neutral 1, in spite of the fact that the gas-phase basicity of 1 is comparable to those of Lys and His. The carbonyl group of 1 acts as a powerful hydrogen-bond acceptor. Within [1+AA+H]+ the side-chain substituents (imidazole group for His and terminal amino group for Lys) present comparable basic properties to those of the α-amino group, taking part to a cooperative hydrogen-bond network. Structural assignment, relying on the comparative analysis of the infrared multiple photon dissociation (IRMPD) spectrum and calculated IR spectra for the candidate geometries, derives from an examination over two frequency ranges: 900-1800 and 2900-3700 cm-1 . Information gained from the latter one proved especially valuable, for example, pointing to the contribution of species characterized by an unperturbed carboxylic OH or imidazole NH stretching mode.


Asunto(s)
Aminoácidos/química , Antineoplásicos/química , Espectrofotometría Infrarroja , Enlace de Hidrógeno , Fotones , Protones , Vibración
14.
Angew Chem Int Ed Engl ; 59(36): 15595-15598, 2020 09 01.
Artículo en Inglés | MEDLINE | ID: mdl-32608165

RESUMEN

Platinum(IV) complexes are extensively studied for their activity against cancer cells as potential substitutes for the widely used platinum(II) drugs. PtIV complexes are kinetically inert and need to be reduced to PtII species to play their pharmacological action, thus acting as prodrugs. The mechanism of the reduction step inside the cell is however still largely unknown. Gas-phase activation of deprotonated platinum(IV) prodrugs was found to generate products in which platinum has a formal +3 oxidation state. IR multiple photon dissociation spectroscopy is thus used to obtain structural information helping to define the nature of both the platinum atom and the ligands. In particular, comparison of calculations at DFT, MP2 and CCSD levels with experimental results demonstrates that the localization of the radical is about equally shared between the dxz orbital of platinum and the pz of nitrogen on the amino group, the latter acting as a non-innocent ligand.

15.
J Mass Spectrom ; 55(11): e4525, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-32368854

RESUMEN

Many plants of the genus Allium are widely cultivated and consumed for their nutraceutical and health-enhancing bioactive components effective in many metabolic and infectious diseases. In particular, Allium sativum L. (garlic), the most economically important Allium species, is known to present volatile, comparatively polar sulfur-containing compounds responsible for both the typical garlic aroma and antimicrobial property. More recently, the (moderately) polar portion of garlic metabolome, rich of polyphenols and amino acids, is gaining increasing interest as a source of antioxidants and primary nutrients. In this study, we have explored the chemical diversity of eight different hydroalcoholic extracts obtained by microwave-assisted extraction of white and red crop A. sativum and wild Allium triquetrum, Allium roseum, and Allium ampeloprasum, all originating from the Mediterranean Basin. The aim is to appraise their potential dietetic and healing value through an in-depth chemical characterization and contribute to preserve and exploit natural resources. The multimethodological method applied here is based on an untargeted metabolic profiling by means of high-resolution electrospray ionization Fourier-transform ion cyclotron resonance (ESI FT-ICR) mass spectrometry. More than 850 by ESI(+) and 450 by ESI(-) putative metabolites have been annotated covering all main classes of primary and secondary metabolites, including amino acids, alkaloids, organic and fatty acids, nucleotides, vitamins, organosulfur compounds, and flavonoids. The pigment and polyphenol components have been separated and quantified by a targeted chromatographic high-performance liquid chromatography-photodiode array detector (HPLC-PDA) and CIEL*a*b* colorimetric assay, showing characteristic yellow and red components in each extract, related to a different milieu of anthocyanins and flavonoids as assigned by high-resolution mass spectrometry (MS).


Asunto(s)
Ajo/química , Metaboloma , Alcaloides/análisis , Aminoácidos/análisis , Cromatografía Líquida de Alta Presión/métodos , Ácidos Grasos/análisis , Flavonoides/análisis , Metabolómica/métodos , Polifenoles/análisis , Espectrometría de Masa por Ionización de Electrospray/métodos , Vitaminas/análisis
16.
J Am Soc Mass Spectrom ; 31(4): 946-960, 2020 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-32233383

RESUMEN

The monofunctional primary complexes cis-[PtCl(NH3)2(L)]+, formed by the reaction of cisplatin, a major chemotherapeutic agent, with four nucleobases L, i.e., uracil (U), 2-thiouracil (2SU), 4-thiouracil (4SU), and 2,4-dithiouracil (24dSU), have been studied by a combination of infrared multiple photon dissociation (IRMPD) action spectroscopy in both the fingerprint (900-1900 cm-1) and the N-H/O-H stretching (3000-3800 cm-1) ranges, energy-resolved collision-induced dissociation (CID) mass spectrometry, and density functional calculations at the B3LYP/LACVP/6-311G** level. On the basis of the comparison across the experimental features and the linear IR spectra of conceivable structures, the cisplatin residue is found to promote a monodentate interaction preferentially with the O4(S4) atoms of the canonical forms of U, 4SU, and 24dSU and to the S2 atom of 2SU, yielding the most stable structures. Additional absorptions reveal the presence of minor, alternative tautomers in the sampled ion populations of 2SU and 24dSU, underlying the ability of cisplatin to increase the prospect of (therapeutically beneficial) nucleic acid strand disorder. Implication of these evidence may provide insights into drug mechanism and design.


Asunto(s)
Cisplatino/metabolismo , Espectrofotometría Infrarroja/métodos , Espectrometría de Masas en Tándem/métodos , Tiouracilo/metabolismo , Uracilo/metabolismo , Antineoplásicos/química , Antineoplásicos/metabolismo , Sitios de Unión , Cisplatino/química , Tiouracilo/análogos & derivados , Uracilo/química
17.
Chemphyschem ; 21(8): 749-761, 2020 04 20.
Artículo en Inglés | MEDLINE | ID: mdl-31951044

RESUMEN

Protonation at the formyl oxygen atom of benzaldehydes leading to the formation of carboxonium ions yields two distinct isomers, depending on the relative orientation of the proton either cis or trans with respect to the hydrogen atom on the adjacent carbon. In this context, the IR multiple photon dissociation (IRMPD) spectra of protonated ortho, meta, and para-hydroxybenzaldehydes (OH-BZH+ ), delivered into the gas phase by electrospray ionization of hydro-alcoholic solutions, are reported in the 3200-3700 cm-1 spectral range. This range is characteristic of O-H stretching modes and thus able to differentiate cis and trans carboxonium isomers. Comparison between IRMPD spectra and DFT calculations at the B3LYP/6-311++G(2df2p) level suggests that for both p-OH-BZH+ and m-OH-BZH+ only cis conformers are present in the ion population analyzed. For o-OH-BZH+ , IRMPD spectroscopy points to a mixture comprising one trans and more than one cis conformers. The energy barrier for cis-trans isomerization calculated for each OH-BZH+ isomer is a measure of the degree of π-electron delocalization. Furthermore, IRMPD spectra of p-OH-BZH+ , m-OH-BZH+ and protonated phenol (this last used as reference) were recorded also in the fingerprint range. Both the observed C-O and O-H stretching vibrations appear to be a measure of π-electron delocalization in the ions.

18.
Chem Rev ; 120(7): 3261-3295, 2020 04 08.
Artículo en Inglés | MEDLINE | ID: mdl-31809038

RESUMEN

Infrared multiple photon dissociation (IRMPD) spectroscopy allows for the derivation of the vibrational fingerprint of molecular ions under tandem mass spectrometry (MS/MS) conditions. It provides insight into the nature and localization of posttranslational modifications (PTMs) affecting single amino acids and peptides. IRMPD spectroscopy, which takes advantage of the high sensitivity and resolution of MS/MS, relies on a wavelength specific fragmentation process occurring on resonance with an IR active vibrational mode of the sampled species and is well suited to reveal the presence of a PTM and its impact in the molecular environment. IRMPD spectroscopy is clearly not a proteomics tool. It is rather a valuable source of information for fixed wavelength IRMPD exploited in dissociation protocols of peptides and proteins. Indeed, from the large variety of model PTM containing amino acids and peptides which have been characterized by IRMPD spectroscopy, specific signatures of PTMs such as phosphorylation or sulfonation can be derived. High throughput workflows relying on the selective fragmentation of modified peptides within a complex mixture have thus been proposed. Sequential fragmentations can be observed upon IR activation, which do not only give rise to rich fragmentation patterns but also overcome low mass cutoff limitations in ion trap mass analyzers. Laser-based vibrational spectroscopy of mass-selected ions holding various PTMs is an increasingly expanding field both in the variety of chemical issues coped with and in the technological advancements and implementations.


Asunto(s)
Péptidos/análisis , Procesamiento Proteico-Postraduccional , Proteínas/análisis , Animales , Humanos , Péptidos/química , Péptidos/metabolismo , Proteínas/química , Proteínas/metabolismo , Espectrofotometría Infrarroja/métodos , Espectrometría de Masas en Tándem , Vibración
19.
J Chem Phys ; 150(16): 165101, 2019 Apr 28.
Artículo en Inglés | MEDLINE | ID: mdl-31042893

RESUMEN

Curcumin (Cur) is a natural polyphenol with a wide spectrum of biological activities and appealing therapeutic potential. Herein, it has been delivered by electrospray ionization as gaseous protonated species, [Cur + H]+, and as a Cu(ii) complex, [Cu(Cur - H)]+, a promising antioxidant and radical scavenger. The gas phase structures were assayed by infrared multiple photon dissociation (IRMPD) spectroscopy in both the fingerprint (800-2000 cm-1) and hydrogen stretching (3100-3750 cm-1) ranges. Comparison between the experimental features and linear IR spectra of the lowest energy structures computed at the B3LYP/6-311+G(d,p) level reveals that bare [Cu(Cur - H)]+ exists in a fully planar and symmetric arrangement, where the metal interacts with the two oxygens of the syn-enolate functionality of deprotonated Cur and both OCH3 groups are engaged in H-bonding with the ortho OH. The effect of protonation on the energetic and geometric determinants of Cur has been explored as well, revealing that bare [Cur + H]+ may exist as a mixture of two close-lying isomers associated with the most stable binding motifs. The additional proton is bound to either the diketo or the keto-enol configuration of Cur, in a bent or nearly planar arrangement, respectively.

20.
Food Chem ; 255: 120-131, 2018 Jul 30.
Artículo en Inglés | MEDLINE | ID: mdl-29571457

RESUMEN

A multi-methodological approach was applied to study red sweet peppers (Capsicum annuum L.) ecotype "Cornetto di Pontecorvo" grown in a greenhouse or in open field. This approach includes morphological analysis, chemical composition determination, and biological activity evaluation of different extracts from pepper fruits. Untargeted analyses, namely NMR spectroscopy and mass spectrometry, allowed the comprehensive pepper metabolite profile of pepper pulp, peel and seeds hydroalcoholic and organic extracts to be determined, showing the presence of sugars, organic acids, amino acids and other secondary metabolites. Targeted analyses, such as HPLC-PDA, HPLC-TLC and spectrophotometric analyses allowed polyphenols, tannins, flavonoids and pigments content to be determined. Samples quality and freshness were verified by the low content of biogenic amines and mycotoxins, as determined using HPLC-FLD and HPLC-MS, respectively. Preliminary biological results demonstrated the ability of the organic extracts to inhibit α-amylase, a key enzyme in the control of glucose metabolism.


Asunto(s)
Capsicum/química , Análisis de los Alimentos/métodos , Extractos Vegetales/farmacología , Antifúngicos/farmacología , Aminas Biogénicas/análisis , Capsicum/metabolismo , Cromatografía Líquida de Alta Presión , Flavonoides/análisis , Calidad de los Alimentos , Frutas/química , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Micotoxinas/análisis , Polifenoles/análisis , Semillas/química , Taninos/análisis , alfa-Amilasas/antagonistas & inhibidores
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