Electron Spin-Polarization Dependent Damage to Chiral Amino Acid l-Histidine

Chirality-Induced Spin Selectivity Enables New Breakthrough in Electrochemical and Photoelectrochemical Reactions

To facilitate the transition from a carbon-energy-dependent society to a sustainable society, conventional engineering strategies, which encounter limitations associated with intrinsic material properties, should undergo the paradigm shift. From a theoretical viewpoint, the spin-dependent feature of oxygen evolution reaction (OER) reveals the potential of a spin-polarization strategy in enhancing the performance of electrochemical (EC) reactions. The chirality-induced spin selectivity (CISS) phenomenon attracts unprecedented attention owing to its potential utility in achieving novel breakthroughs. This paper starts with the experimental results aimed at enhancing the efficiency of the spin-dependent OER focusing on the EC system based on the CISS phenomenon. The applicability of spin-polarization to EC system is verified through various analytical methodologies to clarify the theoretical groundwork and mechanisms underlying the spin-dependent reaction pathway. The discussion is then extended to effective spin-control strategies in photoelectrochemical system based on the CISS effect. Exploring the influence of spin-state control on the kinetic and thermodynamic aspects, this perspective also discusses the effect of spin polarization induced by the CISS phenomenon on spin-dependent OER. Lastly, future directions for enhancing the performance of spin-dependent redox systems are discussed, including expansion to various chemical reactions and the development of materials with spin-control capabilities.

Silver induced chirality controlled spin filtration observed in ss-DNA functionalized with MoS2

Chiral molecules can exhibit strong spin-orbit coupling, which can result in a large spin polarization. This is due to the fact that the energy levels of the electrons in a chiral molecule are strongly influenced by the chiral structure of the molecule, which can result in the separation of the energy levels for electrons with different spin orientations. We report a controlled spin-selective transmission of electrons through 20 base-paired poly-cytosine molecules functionalized with MoS2 flakes on ITO glass via the quantum mechanical tunneling effect. A reversion in spin polarization was observed after the silver ions interact with poly-cytosine due to the strong coordination of Ag(I) with cytosine-cytosine (C-C) mismatches, indicating the formation of duplex structural motifs, as confirmed by the circular dichroism spectroscopy at room temperature. Manipulating the spin of an electron through such a small molecule merely controlled by special cations could pave the way for major advances in spin-independent charge transport, advanced bioanalytical system design, and related applications.

Defective copper-cobalt binuclear Prussian blue analogue nanozymes with high specificity as lytic polysaccharide monooxygenase-mimic via axial ligation of histidine

Degradation of polysaccharides based on lytic polysaccharide monooxygenases (LPMOs) has received considerably interest in the environment and energy fields since 2010. With the rapid development of nanozymes in various fields, it is highly desirable but challenging to develop LPMO-like nanozymes with high specificity and satisfied activity. Here, a defective copper-cobalt binuclear Prussian blue analogue (CuCoPBA) nanozyme was developed via a facile and ingenious methodology based on single histidine (His). For the first time, His-CuCoPBA nanozyme was found to exhibit LPMO-like activity with H2O2 as a cosubstrate at room temperature and neutral pH, which can efficiently catalyze the degradation of galactomannans selectively. Significantly, the high degradation activity at pH 10 expands the application of Fenton-like nanozymes in alkaline condition. Singlet oxygen (1O2), as a main reactive intermediate, plays a crucial role in the galactomannan degradation catalyzed by His-CuCoPBA nanozyme. Both control experimental and density functional theory (DFT) results indicate Cu-NxHis contributes to the efficiently and selectively catalytic activity of His-CuCoPBA nanozymes by emulating the binding and catalytic sites of LPMOs. The present work not only represents a fundamental breakthrough toward degradation of polysaccharide based on nanozyme, but also contributes to understanding the catalytic mechanism of natural Cu-dependent LPMOs.

Surface Bioengineering of Mo2Ga2C MAX Phase to Develop Blended Loose Nanofiltration Membranes for Textile Wastewater Treatment

The potential of blended loose nanofiltration membranes (LNMs) to fractionate dyes and inorganic salts in textile wastewater has become a focus of attention in recent years. In this research work, we fabricated LNMs based on polysulfone (PSf) membranes blended with l-histidine amino acid-functionalized Mo2Ga2C MAX phase (His-MAX). Scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), contact angle, ζ-potential, porosity, and pore size analyses were employed to characterize the LNMs. Blending 0.75 wt % of His-MAX additive with the PSf tailored the LNM's features by making it more water-friendly, increasing its porosity, enlarging its pores, and making its surface smoother. The pure water flux of 127.6 L/m2 h was achieved by LNM containing 0.75 wt % His-MAX, which was 2.5 times greater than the bare one. The mentioned LNM displayed a flux recovery ratio (FRR) of 68.27 and 98.57, 98.31, and 99.7% rejections for Direct red 23, Acid brown 75, and Reactive blue 21 solutions (100 mg/L), respectively. The 0.75 wt % His-MAX LNM could reject 99.1% of dye and 11.5% of salt while maintaining an FRR of 91.19% after four cycles of filtering a binary mixture solution containing Reactive blue 21 and Na2SO4. These findings highlight the potential of the fabricated LNM for desalinating dye solutions.

A search for chiral asymmetry in secondary electron emission from cysteine induced by longitudinally polarized electrons

We performed experiments searching for chirality-dependent secondary electron emission for a 141 eV longitudinally spin-polarized electron beam incident on a thick solid cysteine target. We determined the secondary electron yield by measuring the positive current produced when the cysteine target was negatively biased. No spin-dependent effects to a level of 10-3 were found for the secondary electron emission yield.

Low-Energy Electron Generation for Biomolecular Damage Inquiry: Instrumentation and Methods

Technological advancement has produced a variety of instruments and methods to generate electron beams that have greatly assisted in the extensive theoretical and experimental efforts devoted to investigating the effect of secondary electrons with energies approximately less than 100 eV, which are referred as low-energy electrons (LEEs). In the past two decades, LEE studies have focused on biomolecular systems, which mainly consist of DNA and proteins and their constituents as primary cellular targets of ionizing radiation. These studies have revealed that compared to other reactive species produced by high-energy radiation, LEEs have distinctive pathways and considerable efficiency in inducing lethal DNA lesions. The present work aims to briefly discuss the current state of LEE production technology and to motivate further studies and improvements of LEE generation techniques in relation to biological electron-driven processes associated with such medical applications as radiation therapy and cancer treatment.

Manipulating Electron-Spin Polarization using Cysteine-DNA Chiral Conjugates

The chiral molecules are potential generators of high spin-filters due to their inherent inversion asymmetric helical electric field. We report a controlled spin selective transmission of electrons through self-assembled monolayers of 15 base-paired double-stranded deoxyribonucleic acid (dsDNA) functionalized with two enantiomeric cysteine molecules on gold explored through quantum mechanical tunneling effect. We observed a controlled spin polarization of 33 % with Dextro-cysteine, whereas a mere 8 % with Levo-cysteine molecules using these functionalizations at room temperature. The manipulation of electron's spin merely through such small molecule could lead significant advancement in thespin-dependent charge transport phenomena, and related applications.

Arrow of Time, Entropy, and Protein Folding: Holistic View on Biochirality

Chirality is a universal phenomenon, embracing the space–time domains of non-organic and organic nature. The biological time arrow, evident in the aging of proteins and organisms, should be linked to the prevalent biomolecular chirality. This hypothesis drives our exploration of protein aging, in relation to the biological aging of an organism. Recent advances in the chirality discrimination methods and theoretical considerations of the non-equilibrium thermodynamics clarify the fundamental issues, concerning the biphasic, alternative, and stepwise changes in the conformational entropy associated with protein folding. Living cells represent open, non-equilibrium, self-organizing, and dissipative systems. The non-equilibrium thermodynamics of cell biology are determined by utilizing the energy stored, transferred, and released, via adenosine triphosphate (ATP). At the protein level, the synthesis of a homochiral polypeptide chain of L-amino acids (L-AAs) represents the first state in the evolution of the dynamic non-equilibrium state of the system. At the next step the non-equilibrium state of a protein-centric system is supported and amended by a broad set of posttranslational modifications (PTMs). The enzymatic phosphorylation, being the most abundant and ATP-driven form of PTMs, illustrates the principal significance of the energy-coupling, in maintaining and reshaping the system. However, the physiological functions of phosphorylation are under the permanent risk of being compromised by spontaneous racemization. Therefore, the major distinct steps in protein-centric aging include the biosynthesis of a polypeptide chain, protein folding assisted by the system of PTMs, and age-dependent spontaneous protein racemization and degradation. To the best of our knowledge, we are the first to pay attention to the biphasic, alternative, and stepwise changes in the conformational entropy of protein folding. The broader view on protein folding, including the impact of spontaneous racemization, will help in the goal-oriented experimental design in the field of chiral proteomics.

Investigations into Spin- and Unpolarized Secondary Electron-Induced Reactions in Self-Assembled Monolayers of Cysteine

Cysteine is the simplest thiolated, chiral amino acid and is often used as the anchor for studies of self-assembled monolayers (SAMs) of complex biomolecules such as peptides. Understanding the interaction of SAMs of cysteine with low-energy secondary electrons (SEs) produced by X-rays can further our understanding of radiation damage in biomolecules. In particular, if the electrons are polarized, chiral-selective chemistry could have bearing on the origin of homochirality in nature. In the present paper, we use synchrotron radiation-based X-ray photoelectron spectroscopy to determine the changes that occur in the bonding of self-assembled layers of cysteine on gold as a result of soft X-ray irradiation. To investigate the possibility of chiral selectivity resulting from the interaction of low-energy, spin-polarized SEs (SPSEs), measurements were conducted on cysteine adsorbed on a 3 nm-thick gold layer deposited on a CoPt thin-film multilayer with perpendicular magnetic anisotropy. Time-dependent measurements of the C 1s, N 1s, O 1s, S 2p, and Au 4f core levels are used to follow the changes in surface chemistry and determine reaction cross-sections as a function of SE exposure. Analysis of the data results in cross-sections in the range of 5-7 Mb and suggests possible reaction pathways. Changing the magnetization direction of the CoPt multilayer produces SPSEs with opposite polarity. Some evidence of spin-dependent reactions is indicated but is inconclusive. Possible reasons for the discrepancy are posited.