Molecules

Research

13 pages, 1533 KiB

Open AccessArticle

Surface-Enhanced Raman Spectroscopy on Gold Nanoparticle for Sperm Quality Discrimination

by Yeira P. Lopez-Lora, Nataly J. Galán-Freyle, Natally Vidal-Figueroa, Antony A. Cardozo-Puello, Antonio J. Acosta-Hoyos, Guido Parra-Anaya, Elvin S. Lebrón-Ramírez, Fabián Espitia-Almeida, Samuel P. Hernández-Rivera, Maximiliano Méndez-López, Ornella Fiorillo-Moreno, Karin Rondon-Payare and Leonardo C. Pacheco-Londoño

Molecules 2025, 30(9), 1876; https://doi.org/10.3390/molecules30091876 - 23 Apr 2025

Abstract

Spermatozoa were isolated from the seminal fluid using washing (wash), post-capacitation (POS), and swim-up (SU) techniques, followed by analysis through Surface-Enhanced Raman Spectroscopy (SERS). Density gradient and swim-up methods were applied to 35 semen samples to validate sperm quality. The resulting spectra showed [...] Read more.

Spermatozoa were isolated from the seminal fluid using washing (wash), post-capacitation (POS), and swim-up (SU) techniques, followed by analysis through Surface-Enhanced Raman Spectroscopy (SERS). Density gradient and swim-up methods were applied to 35 semen samples to validate sperm quality. The resulting spectra showed notable variations at 408 cm⁻¹ (S–S stretch attributed to lysozyme) and 728 cm⁻¹ (associated with DNA alterations and methylation). These spectral markers were incorporated into partial least squares discriminant analysis (PLS-DA) models to distinguish among sperm populations prepared by different methods. One PLS-DA model differentiated wash from POS and SU, attaining 86% sensitivity and 91% accuracy. Another model distinguished between POS and SU, achieving 77% sensitivity and 74% accuracy. The combined use of SERS and multivariate analysis offers a promising alternative for assessing sperm quality, supported by motility assessments in 35 validated samples. This approach could enhance both the accuracy and efficiency of reproductive diagnostics. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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17 pages, 3117 KiB

Open AccessArticle

Explosives Analysis Using Thin-Layer Chromatography–Quantum Cascade Laser Spectroscopy

by John R. Castro-Suarez, Luis A. Pérez-Almodóvar, Doris M. Laguer-Martínez, José L. Ruiz-Caballero, José A. Centeno-Ortiz, Tamara Felix-Massa, Leonardo C. Pacheco-Londoño and Samuel P. Hernández-Rivera

Molecules 2025, 30(8), 1844; https://doi.org/10.3390/molecules30081844 - 19 Apr 2025

Viewed by 97

Abstract

A new hyphenated technique using thin-layer chromatography (TLC) to separate analytes in mixtures, coupled with mid-infrared (MIR) laser spectroscopy for identification and quantification, is presented. The method, which provides a means for rapid screening of analytes that is practical, low-cost, fast, robust, and [...] Read more.

A new hyphenated technique using thin-layer chromatography (TLC) to separate analytes in mixtures, coupled with mid-infrared (MIR) laser spectroscopy for identification and quantification, is presented. The method, which provides a means for rapid screening of analytes that is practical, low-cost, fast, robust, and reproducible, was tested using nitroaromatic and aliphatic nitro high explosives (HEs) as target analytes. HEs are anthropogenic contaminants containing an -NO₂ group. For validation of the new technique, a direct comparison of the 2,4,6-trinitrotoluene (TNT) spectrum, obtained by attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy coupled with TLC, was carried out. The MIR laser spectroscopy-based method was evaluated by calculating the analytical figures of merit regarding the calibration curves’ linearity and the method’s sensitivity and precision. The TNT spectrum obtained by the MIR laser method showed two prominent and characteristic bands of the explosive at approximately 1350 cm⁻¹ and 1550 cm⁻¹ compared to the spectrum acquired by ATR-FTIR. The detection limit calculated for TNT was 84 ng, while the quantification limit was 252 ng. Multivariate analysis was used to evaluate the spectroscopic data to identify sources of variation and determine their relation. Partial least squares (PLS) regression analysis and PLS combined with discriminant analysis (PLS-DA) were used for quantification and classification. The new technique, TLC-QCL, is amenable to a smaller footprint with further developments in MIR laser technology, making it portable for fieldwork. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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11 pages, 967 KiB

Open AccessArticle

Terahertz Spectroscopy and Density Functional Theory for Non-Destructive Analysis of Anticoagulant Warfarin

by Jiawei Li, Cong Zhang, Xiaohui Wang, Jinjing Zhang, Hanwen Liu and Xu Wu

Molecules 2025, 30(8), 1791; https://doi.org/10.3390/molecules30081791 - 16 Apr 2025

Viewed by 161

Abstract

Pharmaceutical quality control plays a critical role in safeguarding patient safety and ensuring therapeutic efficacy. However, conventional analytical methods are often hindered by laborious procedures and complex chemical preparation requirements. This study presents a rapid, non-destructive pharmaceutical analysis approach by introducing terahertz spectroscopy [...] Read more.

Pharmaceutical quality control plays a critical role in safeguarding patient safety and ensuring therapeutic efficacy. However, conventional analytical methods are often hindered by laborious procedures and complex chemical preparation requirements. This study presents a rapid, non-destructive pharmaceutical analysis approach by introducing terahertz spectroscopy for the dual-parametric detection of the anticoagulant warfarin. Characteristic absorption peaks of warfarin within the 4–10 THz range were experimentally identified and theoretically resolved through density functional theory calculations, employing both single-molecule and unit cell models. Furthermore, three strong absorption peaks were selected to construct multivariate regression models correlating spectral parameters (peak intensity and area) with warfarin weight, achieving a detection limit of 0.641 mg within a 5 min analytical workflow. This approach enables simultaneous molecular fingerprint identification and quantitative determination without chemical modification, meeting the requirements for the rapid screening of active pharmaceutical ingredients. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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18 pages, 7329 KiB

Open AccessArticle

Visible-Light Photocatalytic Activity of a ZnO-Loaded Isoreticular Metal-Organic Framework

by Ana Y. Rojas-Forero, Laura Y. Hernández-Benítez, María L. Ospina-Castro, Nataly J. Galán-Freyle, John R. Castro-Suarez, Maximiliano Méndez-López, Samuel P. Hernández-Rivera, José A. Centeno-Ortiz, Sandra P. Romero-Nieto and Leonardo C. Pacheco-Londoño

Molecules 2025, 30(6), 1375; https://doi.org/10.3390/molecules30061375 - 19 Mar 2025

Viewed by 336

Abstract

A hybrid material composed of IRMOF-3 and ZnO (IRMOF-3/ZnO) was synthesized to enhance photocatalytic methylene blue (MB) degradation under visible-light irradiation. Scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and diffuse-reflectance UV-Vis analyses confirmed the successful integration of ZnO into the IRMOF-3 framework. [...] Read more.

A hybrid material composed of IRMOF-3 and ZnO (IRMOF-3/ZnO) was synthesized to enhance photocatalytic methylene blue (MB) degradation under visible-light irradiation. Scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and diffuse-reflectance UV-Vis analyses confirmed the successful integration of ZnO into the IRMOF-3 framework. Compared with unmodified IRMOF-3, the hybrid demonstrated superior MB decomposition, as evidenced by faster reaction rate constants and shorter half-lives. Monitoring the MB absorbance at 670 nm (λ_max) revealed more pronounced colorant removal when IRMOF-3/ZnO was exposed to a visible-light source. Diffuse-reflectance UV-Vis spectroscopy showed that IRMOF-3 has a band gap of 2.7 eV, whereas IRMOF-3/ZnO exhibits a slightly higher band gap of 2.8 eV. This modest shift, coupled with the strong interaction between the ZnO semiconductor and the MOF’s amine functionalities, enabled two distinct energy-transfer pathways: intermolecular transfer from IRMOF-3 linkers (acting as visible-light antennas) to ZnO, and intramolecular transfer from Zn to IRMOF-3. Together, these pathways generated abundant free radicals for efficient dye degradation. Despite the necessity for careful synthesis protocols and control of operating conditions to preserve the MOF structure and optimize ZnO loading, the IRMOF-3/ZnO hybrid shows promise as a robust, cost-effective photocatalyst for water-pollutant remediation, taking advantage of the more abundant visible region of solar light. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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29 pages, 10108 KiB

Open AccessArticle

Unveiling the Role of Fractionated Graphene Oxide in Nitric Oxide Scavenging

by Grigoriy R. Chermashentsev, Ivan V. Mikheev, Daria-Mariia V. Ratova, Elena V. Proskurnina and Mikhail A. Proskurnin

Molecules 2025, 30(5), 1069; https://doi.org/10.3390/molecules30051069 - 26 Feb 2025

Cited by 1 | Viewed by 435

Abstract

The feasibility of saturating aqueous anoxic solutions with in situ-generated high-purity nitric oxide (NO) is shown herein. A methemoglobin assay estimated the average nitric oxide concentration to be ca. 20 ± 3 µM. Graphene oxide aqueous dispersions were prepared by ultrasound-assisted extra exfoliation. [...] Read more.

The feasibility of saturating aqueous anoxic solutions with in situ-generated high-purity nitric oxide (NO) is shown herein. A methemoglobin assay estimated the average nitric oxide concentration to be ca. 20 ± 3 µM. Graphene oxide aqueous dispersions were prepared by ultrasound-assisted extra exfoliation. These dispersions, including unpurified (pristine) samples and samples purified from transition metal impurities (bulk) fractions (bulkGO) and (nano) separated fractions (nanoGO) in a range of 0.5 to 14 kDa were prepared with ppm level concentrations. A robust and reproducible chemiluminescence (CL) assay validated the interaction between graphene oxide and NO in a luminol-based system. The results showed a significant increase in NO scavenging activity within the bulkGO fractions to nanofractions ranging from 14 to 3.5 kDa. The different reaction pathways underlying the transformation of nitric oxide are being evaluated, focusing on understanding how its presence or absence affects these processes. Our kinetic model suggests a significant difference in nitric oxide regulation; nanoGO demonstrates an interception rate seventy-times higher than that achieved through CL quenching. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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12 pages, 19545 KiB

Open AccessArticle

Label-Free Surface-Enhanced Raman Scattering for Genomic DNA Cytosine Methylation Reading

by Kazi Morshed Alom, Anastasiia Tukova, Nana Lyu, Alison Rodger and Yuling Wang

Molecules 2025, 30(2), 403; https://doi.org/10.3390/molecules30020403 - 18 Jan 2025

Viewed by 919

Abstract

DNA methylation has been widely studied with the goal of correlating the genome profiles of various diseases with epigenetic mechanisms. Multiple approaches have been developed that employ extensive steps, such as bisulfite treatments, polymerase chain reactions (PCR), restriction digestion, sequencing, mass analysis, etc., [...] Read more.

DNA methylation has been widely studied with the goal of correlating the genome profiles of various diseases with epigenetic mechanisms. Multiple approaches have been developed that employ extensive steps, such as bisulfite treatments, polymerase chain reactions (PCR), restriction digestion, sequencing, mass analysis, etc., to identify DNA methylation. In this article, we report a facile label-free surface-enhanced Raman scattering (SERS) spectroscopy system that utilizes gold nanoparticles (AuNPs) for signal enhancement of methylated DNA. The key innovation of this work is to use anionic nanoparticles at a high ionic strength to introduce the aggregation of AuNPs with anionic DNA. When target methylated DNA is present, the presence of a methyl group in the cytosine C5 position of CpG sites induces a Raman peak at 1350 cm⁻¹. Our amplification-free system has a limit of detection (LOD) of 5% and a limit of quantification (LOQ) of 16% with good specificity. The method was applied to determine the hypermethylated levels of the germline of colorectal cancer cell lines SW48 and SW480. Our simple label-free method holds the potential to read the disease-associated methylation of genomic DNA. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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15 pages, 4411 KiB

Open AccessArticle

Spectroscopic and Quantum Chemical Evidence of Amine–CO₂ and Alcohol–CO₂ Interactions: Confirming an Intriguing Affinity of CO₂ to Monoethanolamine (MEA)

by Sahar Hafizi Yazdabadi, Dmytro Mihrin, Karen Louise Feilberg and René Wugt Larsen

Molecules 2024, 29(23), 5521; https://doi.org/10.3390/molecules29235521 - 22 Nov 2024

Viewed by 862

Abstract

A recent broadband rotational spectroscopic investigation of the cross-association mechanisms of CO₂ with monoethanolamine (MEA) in molecular beams [F. Xie et al., Angew. Chem. Int. Ed., 2023, 62, e202218539] revealed an intriguing affinity of CO₂ to the hydroxy [...] Read more.

A recent broadband rotational spectroscopic investigation of the cross-association mechanisms of CO₂ with monoethanolamine (MEA) in molecular beams [F. Xie et al., Angew. Chem. Int. Ed., 2023, 62, e202218539] revealed an intriguing affinity of CO₂ to the hydroxy group. These findings have triggered the present systematic vibrational spectroscopic exploration of weakly bound amine··CO₂ and alcohol··CO₂ van der Waals cluster molecules embedded in inert “quantum” matrices of neon at 4.2 K complemented by high-level quantum chemical conformational analyses. The non-covalent interactions formed between the amino and hydroxy groups and the electron-deficient carbon atom of CO₂ are demonstrated to lift the degeneracy of the doubly degenerate intramolecular CO₂-bending fundamental significantly with characteristic observed spectral splittings for the amine··CO₂ (≈35–45 cm⁻¹) and alcohol··CO₂ (≈20–25 cm⁻¹) interactions, respectively, despite the almost identically predicted total association energies (≈12–14 kJ·mol⁻¹) for these van der Waals contacts, as revealed by benchmark Domain-based Local Pair Natural Orbital Coupled Cluster DLPNO-CCSD(T) theory. These high-level theoretical predictions reveal significantly higher “geometry preparation energies” for the amine··CO₂ systems leading to a more severe distortion of the CO₂ linearity upon complexation in agreement with the infrared spectroscopic findings. The systematic combined spectroscopic and quantum chemical evidences for cross-association between CO₂ and amines/alcohols in the present work unambiguously confirm an intriguing binding preference of CO₂ to the hydroxy group of the important carbon capture agent MEA, with an accurate vibrational zero-point energy corrected association energy (D₀) of 13.5 kJ·mol⁻¹ at the benchmark DLPNO-CCSD(T)/aug-cc-pV5Z level of theory. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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15 pages, 2523 KiB

Open AccessArticle

Spectral Properties of Marennine-like Pigments Reveal Minor Differences Between Blue Haslea Species and Strains

by Amina Latigui, Boris Jacquette, Jens Dittmer, Jean-François Bardeau, Edouard Boivin, Lucie Beaulieu, Pamela Pasetto and Jean-Luc Mouget

Molecules 2024, 29(22), 5248; https://doi.org/10.3390/molecules29225248 - 6 Nov 2024

Viewed by 905

Abstract

Marennine is the specific bluish pigment produced by the marine diatom Haslea ostrearia Gaillon (Simonsen), responsible for the greening of oysters in France’s Atlantic coast. For decades, H. ostrearia was considered the only blue diatom and described as such. However, new blue Haslea [...] Read more.

Marennine is the specific bluish pigment produced by the marine diatom Haslea ostrearia Gaillon (Simonsen), responsible for the greening of oysters in France’s Atlantic coast. For decades, H. ostrearia was considered the only blue diatom and described as such. However, new blue Haslea species have been described recently, among which Haslea karadagensis Davidovich, Gastineau, and Mouget (Black Sea, Crimea, Ukraine); Haslea provincialis Gastineau, Hansen, and Mouget (Mediterranean Sea, southern France); Haslea silbo Gastineau, Hansen, and Mouget (West Atlantic Ocean, USA); and one not characterized yet, Haslea sp. nov., isolated in Tenerife (Spain). These species produce marennine-like pigments, for which little information is available yet. The present work aims at studying spectral characteristics of these pigments by UV–visible spectrometry, Raman spectrometry, infrared spectrometry, nuclear magnetic resonance, energy-dispersive X-ray spectroscopy, and cyclic voltammetry, and comparing them to those of marennine produced by H. ostrearia strains originating from the north Atlantic Ocean (western France and Macaronesia), and north Pacific Ocean (southwestern USA). Results show that marennine produced by H. ostrearia strains and marennine-like pigments produced by H. provincialis, H. silbo, and Haslea sp. nov. are quite similar regarding their polysaccharide skeleton, and absorption in the UV–visible, infrared, and Raman regions. The most different marennine-like pigment is produced by H. karadagensis, but all Haslea blue pigments studied so far belong to the same family of organic molecules. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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26 pages, 3162 KiB

Open AccessArticle

Ab Initio Manganese Kα and Kβ Energy Eigenvalues, Shake-Off Probabilities, Auger Rates, with Convergence Tests

by Jonathan William Dean, Scott Neil Thompson and Christopher Thomas Chantler

Molecules 2024, 29(17), 4199; https://doi.org/10.3390/molecules29174199 - 4 Sep 2024

Viewed by 962

Abstract

This work presents ab initio calculations for the K

α

spectrum of manganese (Z = 25, [Ar]

3 d^{5} 4 s^{2}

), a highly complex system due to the five open orbitals in the

3 d

shell. The spectrum is composed [...] Read more.

This work presents ab initio calculations for the K

α

spectrum of manganese (Z = 25, [Ar]

3 d^{5} 4 s^{2}

), a highly complex system due to the five open orbitals in the

3 d

shell. The spectrum is composed of the canonical diagram line

[1 s] \to [2 p]

and shake-off satellite lines

[1 s n l] \to [2 p n l]

(

n l \in {2 s, 2 p, 3 s, 3 p, 3 d, 4 s}

), where square brackets denote a hole state. The multiconfiguration Dirac–Hartree–Fock method with the active set approach provides the initial and final atomic wavefunctions. Results are presented as energy eigenvalue spectra for the diagram and satellite transitions. The calculated wavefunctions include over one hundred million configuration state functions and over 280,000 independent transition energies for the seven sets of spectra considered. Shake-off probabilities and Auger transition rates determine satellite intensities. The number of configuration state functions ensures highly-converged wavefunctions. Several measures of convergence demonstrate convergence in the calculated parameters. We obtain convergence of the transition energies in all eight transitions to within 0.06 eV and shake-off probabilities to within 4.5%. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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16 pages, 6315 KiB

Open AccessArticle

A Theoretical Exploration of the Photoinduced Breaking Mechanism of the Glycosidic Bond in Thymine Nucleotide

by Xiao Huang, Yuuichi Orimoto and Yuriko Aoki

Molecules 2024, 29(16), 3789; https://doi.org/10.3390/molecules29163789 - 10 Aug 2024

Viewed by 1298

Abstract

DNA glycosidic bond cleavage may induce cancer under the ultraviolet (UV) effect. Yet, the mechanism of glycosidic bond cleavage remains unclear and requires more detailed clarification. Herein, quantum chemical studies on its photoinduced mechanism are performed using a 5′-thymidine monophosphate (5′-dTMPH) model. In [...] Read more.

DNA glycosidic bond cleavage may induce cancer under the ultraviolet (UV) effect. Yet, the mechanism of glycosidic bond cleavage remains unclear and requires more detailed clarification. Herein, quantum chemical studies on its photoinduced mechanism are performed using a 5′-thymidine monophosphate (5′-dTMPH) model. In this study, four possible paths were examined to study the glycosidic bond cleavage. The results showed that, upon excitation, the electronic transition from the π bonding to π antibonding orbitals of the thymine ring leads to the damage of the thymine ring. Afterwards, the glycosidic bond is cleaved. At first, the doublet ground state (GS) path of glycosidic bond cleavage widely studied by other groups is caused by free electron generated by photoirradiation, with a kinetically feasible energy barrier of ~23 kcal/mol. Additionally, then, the other three paths were proposed that also might cause the glycosidic bond cleavage. The first one is the doublet excited state (ES) path, triggered by free electron along with UV excitation, which can result in a very-high-energy barrier ~49 kcal/mol that is kinetically unfavorable. The second one is the singlet ES path, induced by direct UV excitation, which assumes DNA is directly excited by UV light, which features a very low-energy barrier ~16 kcal/mol that is favored in kinetics. The third one is the triplet ES path, from the singlet state via intersystem crossing (ISC), which refers to a feasible ~27 kcal/mol energy barrier. This study emphasizes the pivotal role of the DNA glycosidic bond cleavage by our proposed direct UV excitation (especially singlet ES path) in addition to the authorized indirect free-electron-induced path, which should provide essential insights to future mechanistic comprehension and novel anti-cancer drug design. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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16 pages, 2863 KiB

Open AccessArticle

QCL Infrared Spectroscopy Combined with Machine Learning as a Useful Tool for Classifying Acetaminophen Tablets by Brand

by José A. Martínez-Trespalacios, Daniel E. Polo-Herrera, Tamara Y. Félix-Massa, Samuel P. Hernandez-Rivera, Joaquín Hernandez-Fernandez, Fredy Colpas-Castillo and John R. Castro-Suarez

Molecules 2024, 29(15), 3562; https://doi.org/10.3390/molecules29153562 - 28 Jul 2024

Viewed by 1880

Abstract

The development of new methods of identification of active pharmaceutical ingredients (API) is a subject of paramount importance for research centers, the pharmaceutical industry, and law enforcement agencies. Here, a system for identifying and classifying pharmaceutical tablets containing acetaminophen (AAP) by brand has [...] Read more.

The development of new methods of identification of active pharmaceutical ingredients (API) is a subject of paramount importance for research centers, the pharmaceutical industry, and law enforcement agencies. Here, a system for identifying and classifying pharmaceutical tablets containing acetaminophen (AAP) by brand has been developed. In total, 15 tablets of 11 brands for a total of 165 samples were analyzed. Mid-infrared vibrational spectroscopy with multivariate analysis was employed. Quantum cascade lasers (QCLs) were used as mid-infrared sources. IR spectra in the spectral range 980–1600 cm⁻¹ were recorded. Five different classification methods were used. First, a spectral search through correlation indices. Second, machine learning algorithms such as principal component analysis (PCA), support vector classification (SVC), decision tree classifier (DTC), and artificial neural network (ANN) were employed to classify tablets by brands. SNV and first derivative were used as preprocessing to improve the spectral information. Precision, recall, specificity, F1-score, and accuracy were used as criteria to evaluate the best SVC, DEE, and ANN classification models obtained. The IR spectra of the tablets show characteristic vibrational signals of AAP and other APIs present. Spectral classification by spectral search and PCA showed limitations in differentiating between brands, particularly for tablets containing AAP as the only API. Machine learning models, specifically SVC, achieved high accuracy in classifying AAP tablets according to their brand, even for brands containing only AAP. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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14 pages, 2295 KiB

Open AccessArticle

The Role of Ovalbumin in Manganese Homeostasis during Chick Embryogenesis: An EPR Spectroscopic Study

by Ana Vesković, Aleksandra M. Bondžić and Ana Popović Bijelić

Molecules 2024, 29(13), 3221; https://doi.org/10.3390/molecules29133221 - 7 Jul 2024

Viewed by 1389

Abstract

Ovalbumin (OVA), a protein vital for chick embryo nutrition, hydration, and antimicrobial protection, together with other egg-white proteins, migrates to the amniotic fluid and is orally absorbed by the embryo during embryogenesis. Recently, it has been shown that for optimal eggshell quality, the [...] Read more.

Ovalbumin (OVA), a protein vital for chick embryo nutrition, hydration, and antimicrobial protection, together with other egg-white proteins, migrates to the amniotic fluid and is orally absorbed by the embryo during embryogenesis. Recently, it has been shown that for optimal eggshell quality, the hen diet can be supplemented with manganese. Although essential for embryonic development, manganese in excess causes neurotoxicity. This study investigates whether OVA may be involved in the regulation of manganese levels. The binding of Mn(II) to OVA was investigated using electron paramagnetic resonance (EPR) spectroscopy. The results show that OVA binds a maximum of two Mn(II) ions, one with slightly weaker affinity, even in a 10-fold excess, suggesting it may have a protective role from Mn(II) overload. It seems that the binding of Mn(II), or the presence of excess Mn(II), does not affect OVA’s tertiary structure, as evidenced from fluorescence and UV/vis measurements. Comparative analysis with bovine and human serum albumins revealed that they exhibit higher affinities for Mn(II) than OVA, most likely due to their essentially different physiological roles. These findings suggest that OVA does not play a role in the transport and storage of manganese; however, it may be involved in embryo protection from manganese-induced toxicity. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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14 pages, 3258 KiB

Open AccessArticle

Insights into Halogen-Induced Changes in 4-Anilinoquinazoline EGFR Inhibitors: A Computational Spectroscopic Study

by Sallam Alagawani, Vladislav Vasilyev, Andrew H. A. Clayton and Feng Wang

Molecules 2024, 29(12), 2800; https://doi.org/10.3390/molecules29122800 - 12 Jun 2024

Cited by 1 | Viewed by 1251

Abstract

The epidermal growth factor receptor (EGFR) is a pivotal target in cancer therapy due to its significance within the tyrosine kinase family. EGFR inhibitors like AG-1478 and PD153035, featuring a 4-anilinoquinazoline moiety, have garnered global attention for their potent therapeutic activities. While pre-clinical [...] Read more.

The epidermal growth factor receptor (EGFR) is a pivotal target in cancer therapy due to its significance within the tyrosine kinase family. EGFR inhibitors like AG-1478 and PD153035, featuring a 4-anilinoquinazoline moiety, have garnered global attention for their potent therapeutic activities. While pre-clinical studies have highlighted the significant impact of halogen substitution at the C3’-anilino position on drug potency, the underlying mechanism remains unclear. This study investigates the influence of halogen substitution (X = H, F, Cl, Br, I) on the structure, properties, and spectroscopy of halogen-substituted 4-anilinoquinazoline tyrosine kinase inhibitors (TKIs) using time-dependent density functional methods (TD-DFT) with the B3LYP functional. Our calculations revealed that halogen substitution did not induce significant changes in the three-dimensional conformation of the TKIs but led to noticeable alterations in electronic properties, such as dipole moment and spatial extent, impacting interactions at the EGFR binding site. The UV–visible spectra show that more potent TKI-X compounds typically have shorter wavelengths, with bromine’s peak wavelength at 326.71 nm and hydrogen, with the lowest IC50 nM, shifting its lambda max to 333.17 nm, indicating a correlation between potency and spectral characteristics. Further analysis of the four lowest-lying conformers of each TKI-X, along with their crystal structures from the EGFR database, confirms that the most potent conformer is often not the global minimum structure but one of the low-lying conformers. The more potent TKI-Cl and TKI-Br exhibit larger deviations (RMSD > 0.65 Å) from their global minimum structures compared to other TKI-X (RMSD < 0.15 Å), indicating that potency is associated with greater flexibility. Dipole moments of TKI-X correlate with drug potency (ln(IC50 nM)), with TKI-Cl and TKI-Br showing significantly higher dipole moments (>8.0 Debye) in both their global minimum and crystal structures. Additionally, optical spectral shifts correlate with potency, as TKI-Cl and TKI-Br exhibit blue shifts from their global minimum structures, in contrast to other TKI-X. This suggests that optical reporting can effectively probe drug potency and conformation changes. Full article

(This article belongs to the Special Issue Molecular Spectroscopy in Applied Chemistry)

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