Infrared and Raman spectroscopic investigation of the reaction mechanism of cytochrome c oxidase

Curcumin promotes oligodendrocyte differentiation and their protection against TNF-α through the activation of the nuclear receptor PPAR-γ

Curcumin is a compound found in the rhizome of Curcuma longa (turmeric) with a large repertoire of pharmacological properties, including anti-inflammatory and neuroprotective activities. The current study aims to assess the effects of this natural compound on oligodendrocyte progenitor (OP) differentiation, particularly in inflammatory conditions. We found that curcumin can promote the differentiation of OPs and to counteract the maturation arrest of OPs induced by TNF-α by a mechanism involving PPAR-γ (peroxisome proliferator activated receptor), a ligand-activated transcription factor with neuroprotective and anti-inflammatory capabilities. Furthermore, curcumin induces the phosphorylation of the protein kinase ERK1/2 known to regulate the transition from OPs to immature oligodendrocytes (OLs), by a mechanism only partially dependent on PPAR-γ. Curcumin is also able to raise the levels of the co-factor PGC1-α and of the cytochrome c oxidase core protein COX1, even when OPs are exposed to TNF-α, through a PPAR-γ-mediated mechanism, in line with the known ability of PPAR-γ to promote mitochondrial integrity and functions, which are crucial for OL differentiation to occur. Altogether, this study provides evidence for a further mechanism of action of curcumin besides its well-known anti-inflammatory properties and supports the suggested therapeutic potential of this nutraceutical in demyelinating diseases.

Molecular understanding of heteronuclear active sites in heme-copper oxidases, nitric oxide reductases, and sulfite reductases through biomimetic modelling

Heme-copper oxidases (HCO), nitric oxide reductases (NOR), and sulfite reductases (SiR) catalyze the multi-electron and multi-proton reductions of O2, NO, and SO32-, respectively. Each of these reactions is important to drive cellular energy production through respiratory metabolism and HCO, NOR, and SiR evolved to contain heteronuclear active sites containing heme/copper, heme/nonheme iron, and heme-[4Fe-4S] centers, respectively. The complexity of the structures and reactions of these native enzymes, along with their large sizes and/or membrane associations, make it challenging to fully understand the crucial structural features responsible for the catalytic properties of these active sites. In this review, we summarize progress that has been made to better understand these heteronuclear metalloenzymes at the molecular level though study of the native enzymes along with insights gained from biomimetic models comprising either small molecules or proteins. Further understanding the reaction selectivity of these enzymes is discussed through comparisons of their similar heteronuclear active sites, and we offer outlook for further investigations.

A proof of concept 'phase zero' study of neurodevelopment using brain organoid models with Vis/near-infrared spectroscopy and electrophysiology

Homeostatic control of neuronal excitability by modulation of synaptic inhibition (I) and excitation (E) of the principal neurons is important during brain maturation. The fundamental features of in-utero brain development, including local synaptic E-I ratio and bioenergetics, can be modeled by cerebral organoids (CO) that have exhibited highly regular nested oscillatory network events. Therefore, we evaluated a 'Phase Zero' clinical study platform combining broadband Vis/near-infrared(NIR) spectroscopy and electrophysiology with studying E-I ratio based on the spectral exponent of local field potentials and bioenergetics based on the activity of mitochondrial Cytochrome-C Oxidase (CCO). We found a significant effect of the age of the healthy controls iPSC CO from 23 days to 3 months on the CCO activity (chi-square (2, N = 10) = 20, p = 4.5400e-05), and spectral exponent between 30-50 Hz (chi-square (2, N = 16) = 13.88, p = 0.001). Also, a significant effect of drugs, choline (CHO), idebenone (IDB), R-alpha-lipoic acid plus acetyl-L-carnitine (LCLA), was found on the CCO activity (chi-square (3, N = 10) = 25.44, p = 1.2492e-05), spectral exponent between 1 and 20 Hz (chi-square (3, N = 16) = 43.5, p = 1.9273e-09) and 30-50 Hz (chi-square (3, N = 16) = 23.47, p = 3.2148e-05) in 34 days old CO from schizophrenia (SCZ) patients iPSC. We present the feasibility of a multimodal approach, combining electrophysiology and broadband Vis-NIR spectroscopy, to monitor neurodevelopment in brain organoid models that can complement traditional drug design approaches to test clinically meaningful hypotheses.

Tailoring Cu substituted hydroxyapatite/functionalized multiwalled carbon nanotube composite coating on 316L SS implant for enhanced corrosion resistance, antibacterial and bioactive properties

The aim of the present work is to study the potential change in the antibacterial properties of Cu-hydroxyapatite/functionalized multiwall carbon nanotube (HA/f-MWCNT) composite coated heterogeneous implant surfaces against Gram positive and Gram-negative microorganism and to reveal the possible contribution of surface corrosion effects arising in stimulated body fluid. Novel spray pyrolysis instrument designed with double nozzle was used for the fabrication of Cu-hydroxyapatite/f-MWCNT film on 316L stainless steel (SS). The Cu-hydroxyapatite/MWCNT coated bioimplant was characterized by a series of techniques to identify the crystallinity, chemical bonds, surface morphology and elemental composition. The results disclose that the coated implants exhibit highly crystalline nature with the space group of P6_3mc and spherical shaped morphology. The corrosion current density revealed a remarkable decrease from 6.8 to 3.8 μA suggesting that the Cu substituted hydroxyapatite/f-MWCNT composite coating provided higher barrier properties which is beneficial to achieve higher corrosion protection of 316L SS implant. The hybrid Cu-hydroxyapatite-MWCNT composite revealed better antibacterial ability than HA/MWCNT for both gram positive and gram-negative bacteria with a maximum inhibition zone of 13-17 mm, compared with hydroxyapatite/f-MWCNT. The antibacterial ability of the Cu-hydroxyapatite/f-MWCNT nanocomposites was effective against Escherichia coli compared with other microorganisms. The Cu-hydroxyapatite/f-MWCNT nanocomposite exhibited that the coated material is nontoxic, biocompatible and suitable for biomedical application.

Infrared Difference Spectroscopy of Proteins: From Bands to Bonds

Infrared difference spectroscopy probes vibrational changes of proteins upon their perturbation. Compared with other spectroscopic methods, it stands out by its sensitivity to the protonation state, H-bonding, and the conformation of different groups in proteins, including the peptide backbone, amino acid side chains, internal water molecules, or cofactors. In particular, the detection of protonation and H-bonding changes in a time-resolved manner, not easily obtained by other techniques, is one of the most successful applications of IR difference spectroscopy. The present review deals with the use of perturbations designed to specifically change the protein between two (or more) functionally relevant states, a strategy often referred to as reaction-induced IR difference spectroscopy. In the first half of this contribution, I review the technique of reaction-induced IR difference spectroscopy of proteins, with special emphasis given to the preparation of suitable samples and their characterization, strategies for the perturbation of proteins, and methodologies for time-resolved measurements (from nanoseconds to minutes). The second half of this contribution focuses on the spectral interpretation. It starts by reviewing how changes in H-bonding, medium polarity, and vibrational coupling affect vibrational frequencies, intensities, and bandwidths. It is followed by band assignments, a crucial aspect mostly performed with the help of isotopic labeling and site-directed mutagenesis, and complemented by integration and interpretation of the results in the context of the studied protein, an aspect increasingly supported by spectral calculations. Selected examples from the literature, predominately but not exclusively from retinal proteins, are used to illustrate the topics covered in this review.

Probing Structure and Reaction Dynamics of Proteins Using Time-Resolved Resonance Raman Spectroscopy

The mechanistic understanding of protein functions requires insight into the structural and reaction dynamics. To elucidate these processes, a variety of experimental approaches are employed. Among them, time-resolved (TR) resonance Raman (RR) is a particularly versatile tool to probe processes of proteins harboring cofactors with electronic transitions in the visible range, such as retinal or heme proteins. TR RR spectroscopy offers the advantage of simultaneously providing molecular structure and kinetic information. The various TR RR spectroscopic methods can cover a wide dynamic range down to the femtosecond time regime and have been employed in monitoring photoinduced reaction cascades, ligand binding and dissociation, electron transfer, enzymatic reactions, and protein un- and refolding. In this account, we review the achievements of TR RR spectroscopy of nearly 50 years of research in this field, which also illustrates how the role of TR RR spectroscopy in molecular life science has changed from the beginning until now. We outline the various methodological approaches and developments and point out current limitations and potential perspectives.

Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function

Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H+/4e- reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements. This review encompasses important aspects of heme-O2 and copper-O2 (bio)chemistries as they relate to the design and interpretation of small molecule model systems and provides perspectives from fundamental coordination chemistry, which can be applied to the understanding of HCO activity. We focus on recent advancements from studies of heme-Cu models, evaluating experimental and computational results, which highlight important fundamental structure-function relationships. Finally, we provide an outlook for future potential contributions from synthetic inorganic chemistry and discuss their implications with relevance to biological O2-reduction.

The tuning of the plasmon resonance of the metal nanoparticles in terms of the SERS effect

The Surface-enhanced Raman spectroscopy is the essential tool for various levels of the molecular studies. In order to become widely used as a fast analytical tool, the enhancing structures such as the nanoparticles have to be simple, inexpensive, and offer good flexibility in enhancing properties and the spectral range. In this paper, we investigated the plasmonic properties of the metal nanoparticles, to which the molecules of interest can be adsorbed, forming the bionanocomplexes. Here, for the first time, we provided the collection of the results gathered in one article, which can serve as the basis or guidance for designing the SERS studies on different bionanocomplexes, various nanoparticle structures, sizes, and excitation wavelengths. The presented plasmonic properties describe the spectral position of the plasmonic resonances as results of their size and structure. The electric field enhancement as a key contributor to the SERS effect is given as well. We considered silver and gold nanoparticles and their variations. Gold is one of the best choice, due to its relevant surface properties, however, suffers from the plasmonic activity and rather static spectral position of the plasmonic resonances. Therefore, one of the main purposes was to show the effective resonance tuning using simple and less expensive geometries. We showed the possibility to adjust the plasmonic resonances with the excitation wavelengths from the blue region to the near infrared region of lasers most commonly used for Raman spectroscopy. The presented studies indicated the high potential of the core-shell structures for this kind of applications.

Charge Distribution Dependent Spectral Analysis of the Oxidized Diferrocenyl-Oligothienylene-Vinylene Molecular Wires

The vibrational spectra have been investigated for revealing the comprehensive structure of diferrocenyl-oligothienylene-vinylene complex, stimulated by the excellent experimental reports [group of Casado J. Am. Chem. Soc. 2012, 134, 12, 5675]. The IR and Raman spectra were simulated. It is found that the change of charge distribution and bond length are associated with the variation in the frequencies of specific vibration in infrared spectra for the neutral and radical oxidation states. The theoretical simulation of charge difference density indicate that charge transfer mechanism for neutral and dication states are significant different. The results can offer hints for the rational design of novel and interesting oligomer semiconductor.

Hydrogen bonding plays a significant role in the binding of coomassie brilliant blue-R to hemoglobin: FT-IR, fluorescence and molecular dynamics studies

Coomassie brilliant blue-R (CBB-R) specifically binds to bovine hemoglobin with a stoichiometric ratio of 1 : 1.