Electrochemical Potential Difference Research Articles

The Pivotal Function of SLC16A1 and SLC16A1-AS1 in Cancer Progress: Molecular Pathogenesis and Prognosis.

More than 300 membranes make up the SLC family of transporters, utilizing an ion gradient or electrochemical potential difference to move their substrates across biological membranes. The SLC16 gene family contains fourteen members. Proton-linked transportation of monocarboxylates can be promoted by the transporters MCT1, which the SLC16A1 gene family encodes. Glycolysis is constitutively up-regulated in cancer cells, and the amount of lactate produced as a result is correlated with prognosis. Further speaking, SLC16A1 plays an essential role in controlling the growth and spread of tumors, according to mounting evidence. Additionally, LncRNAs are the collective term for all genes that produce RNA transcripts longer than 200 nucleotides but do not convert into proteins. It has steadily developed into a hub for research, offering an innovative approach to tumor study as technology related to molecular biology advances. The growing study has uncovered SLC16A1-AS1, an RNA that acts as an antisense to SLC16A1, which is erroneously expressed in various types of cancers. Therefore, we compiled the most recent information on the physiological functions and underlying processes of SLC16A1 and the LncRNA SLC16A1-AS1 during tumor development to explore their impact on cancer treatment and prognosis. We compiled the most recent information on the physiological functions and underlying processes of SLC16A1 and the LncRNA SLC16A1-AS1 during tumor development to explore their impact on cancer treatment and prognosis. Relevant studies were retrieved and collected through the PubMed system. After determining SLC16A1 and SLC16A1-AS1 as the research object, we found a close relationship between SLC16A1 and tumorigenesis as well as the influencing factors through the analysis of the research articles. SLC16A1 regulates lactate chemotaxis while uncovering SLC16A1- AS1 as an antisense RNA acting through multiple pathways; they affect the metabolism of tumor cells and have an impact on the prognosis of patients with various cancers.

Tunneling Mechanisms of Quinones in Photosynthetic Reaction Center–Light Harvesting 1 Supercomplexes

In photosynthesis, light energy is absorbed and transferred to the reaction center, ultimately leading to the reduction of quinone molecules through the electron transfer chain. The oxidation and reduction of quinones generate an electrochemical potential difference used for adenosine triphosphate synthesis. The trafficking of quinone/quinol molecules between electron transport components has been a long‐standing question. Here, an atomic‐level investigation into the molecular mechanism of quinol dissociation in the photosynthetic reaction center–light‐harvesting complex 1 (RC–LH1) supercomplexes from Rhodopseudomonas palustris, using classical molecular dynamics (MD) simulations combined with self‐random acceleration MD‐MD simulations and umbrella sampling methods, is conducted. Results reveal a significant increase in the mobility of quinone molecules upon reduction within RC–LH1, which is accompanied by conformational modifications in the local protein environment. Quinol molecules have a tendency to escape from RC–LH1 in a tail‐first mode, exhibiting channel selectivity, with distinct preferred dissociation pathways in the closed and open LH1 rings. Furthermore, comparative analysis of free energy profiles indicates that alternations in the protein environment accelerate the dissociation of quinol molecules through the open LH1 ring. In particular, aromatic amino acids form π‐stacking interactions with the quinol headgroup, resembling the key components in a conveyor belt system. This study provides insights into the molecular mechanisms that govern quinone/quinol exchange in bacterial photosynthesis and lays the framework for tuning electron flow and energy conversion to improve metabolic performance.

(Invited) Changes in Electric Double-Layer Structures Under Localized Surface Plasmon Excitation

For the visible light energy conversion, the localized surface plasmon resonance (LSPR), which is the collective oscillations of free electrons, should be promising. With the excitation of LSPR, the highly localized electric field generates in the vicinity of metal nanostructures. It is interesting that various unique photo-response properties, such as chemical reactions or molecular excitations, can be observed due to the enhancement of light-matter interaction.[1] To understand and control such mediated chemical reactions or electrochemical reactions, the precise understanding about the electrified interfaces of plasmonic nanostructures should be required.Especially in the electrochemical system, the electric double layer is formed due to the difference in electrochemical potential between the metal interface and solution. The study of the surface potential is important for the design of chemical reactions because the surface potential at the liquid-solid interface is dependent on the physical properties of the systems. The zeta potential which is the potential of the slipping surface near the Stern layer of the diffusion layer could provide such information. From this point of view, in this study, we investigated the electric double-layer structures through the examination of the zeta potential under LSPR excitation condition. To obtain the zeta potential, we have performed the streaming potential method using Au nanoisland structures under visible light illuminations to excite the LSPR. It was interesting that the zeta potential was drastically changes under the visible light illumination conditions. This zeta potential change indicates the changes in the electric double layer structures through the excitation of LSPR. Through the investigations of incident wavelength dependence or the substrate dependences, the effects for the LSPR excitations on the electric double layer structure have been revealed. The present work would provide the fundamental knowledge about the effect on the LSPR excitation at solid-liquid interfaces.[1] H. Minamimoto et al., Acc. Chem. Res., 2022, 55(6), 809.

(Invited) A Hybrid Electrochemical and Catalytic Compression System for Direct Generation of High-Pressure Hydrogen at 350 Atmospheric Pressure

Hydrogen is becoming the center piece in the global de-carbonatization efforts in multiple industrial sectors. Gaseous hydrogen at high pressures in gas tanks is the most common approach for H2 storage, transportation and hydrogen refueling for fuel cell vehicles. Gaseous hydrogen at high pressures is also heavily used in the Haber process for ammonia production and hydro-cracking of heavy petroleum. In the long term, low-cost high pressure H2 will also play a critical role in the future long-duration grid storage for deep decarbonization and improved resilience.In this talk, I will share some recent development on a hybrid electrochemical/catalytic approach for direct generation of high-pressure H2 in collaboration with Pacific Northwest National Laboratory (PNNL). The hybrid system oxidizes water to oxygen at the anode, reduces V3+ to V2+ at the cathode, and stores proton in the catholyte during the “electrochemical charging” step. We demonstrated that the charged catholyte is then capable of generating H2 at >350 bar in the subsequent “catalytic discharging” step without any additional energy input. This concept leverages the electrochemical Nernst potential difference between the redox couple (V2+/3+) and the hydrogen evolution reaction and delivers a unique system that is capable of generating H2 at demand and at high pressure without any mechanical or electrochemical compression. We estimate a cost of <$0.19/kg-H2 for compression, representing >80% of the cost reduction compared to the traditional multi-stage compressor approach.

A Study on the Correlation between Applied Electricity and Electrochemical Desulfurization of Liquid Iron By Molten Slag

Based on the electrochemical character of the desulfurization of liquid iron by molten slag, a previous study reported that applying electricity could enhance the desulfurization. The authors have investigated the mechanism of electrochemical desulfurization and its practical feasibility in terms of reaction rate and electricity efficiency. Nevertheless, the quantitative relationship between electricity and desulfurization still needs to be comprehended. The present study attempted the correlation by carrying out a series of electrochemical desulfurization experiments and thermodynamic calculations. Experiments were designed in a two-step sequence: the first was the normal desulfurization of a liquid iron containing C and S by CaO-Al2O3-MgOsat. slags without applied electricity, and the second was the subsequent electrochemical desulfurization with various electric currents. A graphite disc was put on the surface of the slag and connected with Mo wire to a DC power supply to supply electricity to the system. All the experiments were conducted in the induction furnace at 1400 °C under a CO gas atmosphere. At predetermined times, a certain amount of the iron and slag was sampled and analyzed using the C/S combustion method (LECO CS844) for S contents in both phases. The results were interpreted by employing the Nernst equation to extract the potential difference ∆𝜙S for the electrochemical desulfurization. It was assumed that 1) ∆𝜙S was an electrochemical potential difference to enhance the electrochemical desulfurization, 2) potential differences due to the electrochemical reaction and others (the electric resistance over the slag, iron, etc.) are added to the overall voltage difference observed. It was found that applying electric current (I) to the liquid iron and the molten slag increased the final S distribution ratio between the two phases, the so-called L S (consequently ∆𝜙S increased). When the I was kept constant during each experiment, increasing C/A (= %CaO/%Al2O3) decreased R DeS (= ∆𝜙S / I). For a given C/A, R DeS was independent of the applied I within the range of the I, so the electric properties of the slag might influence it. A previous study reported that the electrical conductivity of a similar slag was increased by increasing the C/A of the slag. Therefore, increasing C/A in the present study increased the electrical conductivity of the slag (𝜎) and decreased the resistance of the slag. It was in the same direction as the R DeS. In the present study, the obtained ∆𝜙S was also predicted by applying the Nernst equation along with a thermodynamic model for liquid iron and sulfide dissolved in molten slag. The enhanced desulfurization by the electricity was interpreted as increasing activity of CaS in the slag and decreasing activity of S in the liquid iron. Accordingly, the predicted ∆𝜙S increased with increasing current under all slag conditions, which was in good agreement with the experimental data. The model is expected to predict the necessary current level for a desired electrochemical desulfurization.

Advanced ion-selective wood membranes: Leveraging aligned cellulose nanofibers for enhanced osmotic energy conversion

Nanofluidic reverse electrodialysis (RED) is widely recognized as an exceptionally effective method for harvesting osmotic energy. Nevertheless, its progress has been impeded by the high costs and intricate fabrication processes associated with the required ion exchange membranes. The ion-selective wood membranes (ISWM) are derived directly from natural wood through a meticulously designed two-step chemical modification and densification process. The obtained ISWM with a highly charged surface effectively preserves the alignment of nanochannels from the cellulose fibers sourced in natural wood. Moreover, the laminated structure consisting of oriented nanofibers enhances ion conductivity by a factor of 4 compared to natural wood birch under low KCl concentrations. The charged and aligned nanochannels serve as nanofluidic conduits, facilitating selective ion transport. This, in turn, engenders efficient charge separation and the generation of an electrochemical potential difference. In energy harvesting systems such as ISWM-RED, the synergistic interplay between the electrochemical potential difference and ionic flux manifests in a remarkable output power density, reaching up to 658 mW m−2 to a salinity gradient of KCl at a magnitude of 50-fold. ISWM is an outstanding nanofluidic material that provides a cost-effective and easy-to-prepare solution for producing natural nanofluidic materials. Our investigation delineates a promising trajectory for developing high-performance nanofluidic RED devices tailored for efficient osmotic energy harvesting from renewable and abundant natural resources.

Influence of Starch Admixtures and Silver Colloids Stabilised with Starch Hydrolysates on the Course of Electrochemical Potential Difference of Reinforcing Steel in High-chloride Environment

The purpose of the conducted study was to verify whether the use of concrete admixtures with modified starches and starches modified with stabilised silver colloids affects the course of electrochemical potential difference, and hence corrosion, of reinforcing steel in a chloride environment. In the tests, cross-linked starches and products of acid hydrolysis of starch (dextrins) were used as admixtures. The 1-molar aqueous solution of sodium chloride was used as an aggressive environment. The tests consisted of measuring the potential difference generated in the reinforcement corrosion cell on the surface for a period of 60 days and then assessing the risk of corrosion. The effect of the addition of starch derivatives on the properties of cement paste was investigated through a one-way ANOVA analysis of variance followed by post hoc tests. The test results showed that the use of concrete admixtures with cross-linked starches positively affects the passivation of the steel. The likelihood of reinforcing steel corrosion when using distarch phosphate, acetylated distarch phosphate and acetylated distarch adipate admixtures is less than 5%. The results obtained showed an improved effect on the passivation of reinforcing steel in cement composites. Additionally, concrete samples may have microbicidal properties.

Fe/Au galvanic nanocells to generate self-sustained Fenton reactions without additives at neutral pH.

The generation of reactive oxygen species (ROS) via the Fenton reaction has received significant attention for widespread applications. This reaction can be triggered by zero-valent metal nanoparticles by converting externally added H2O2 into hydroxyl radicals (˙OH) in acidic media. To avoid the addition of external additives or energy supply, developing self-sustained catalytic systems enabling onsite production of H2O2 at a neutral pH is crucial. Here, we present novel galvanic nanocells (GNCs) based on metallic Fe/Au bilayers on arrays of nanoporous silica nanostructures for the generation of self-sustained Fenton reactions. These GNCs exploit the large electrochemical potential difference between the Fe and Au layers to enable direct H2O2 production and efficient release of Fe2+ in water at neutral pH, thereby triggering the Fenton reaction. Additionally, the GNCs promote Fe2+/Fe3+ circulation and minimize side reactions that passivate the iron surface to enhance their reactivity. The capability to directly trigger the Fenton reaction in water at pH 7 is demonstrated by the fast degradation and mineralization of organic pollutants, by using tiny amounts of catalyst. The self-generated H2O2 and its transformation into ˙OH in a neutral environment provide a promising route not only in environmental remediation but also to produce therapeutic ROS and address the limitations of Fenton catalytic nanostructures.

Synthesis and Characterization of Vitrimer-like Self-Healing Polymer Electrolytes for Lithium Metal Batteries

Solid-polymer electrolytes have become crucially significant with the fast-expanding energy requirements in both the academic and industrial spheres due to their better safety and energy density compared to liquid electrolytes. Despite these encouraging possibilities, a few obstacles are associated with these electrolytes, chief among them being the limited charge transport via the solid electrode-electrolyte interface. Due to the difference in electrochemical potential between the electrode and the electrolyte, this obstruction initiates electrode-electrolyte interactions through electrode volumetric changes, interface reactions, and space charge layers.One possible way to enhance the LIB performance could be by integrating a new class of covalent adaptable networks called vitrimers.The self-healing, shape memory, recyclability, and reprocessibility properties of vitrimers, a class of covalent adaptable networks (CANs), are derived from a covalent molecular network that can change its topology through molecular rearrangements while maintaining the overall number of network bonds. In this manner, Li dendrites that might develop during battery cycling could be eliminated and the electrolyte-electrode contact could be restored by vitrimers. Figure 1

Enhancement of Metal Nanostructure Deposition on Silicon Laser-Induced Periodic Surface Structures by Galvanic Replacement.

We report a chemically motivated, single-step method to enhance metal deposition onto silicon laser-induced periodic surface structures (LIPSSs) using reactive laser ablation in liquid (RLAL). Galvanic replacement (GR) reactions were used in conjunction with RLAL (GR-RLAL) to promote the deposition of Au and Cu nanostructures onto a Si LIPSS. To increase the deposition of Au, sacrificial metals Cu, Fe, and Zn were used; Fe and Zn also enhanced the deposition of Cu. We show that the deposited metal content, surface morphology, and metal crystallite size can be tuned based on the difference in electrochemical potentials of the deposited and sacrificial metal. Compared to the Au and Cu reference samples, GR more than doubled the metal content on the LIPSS and reduced metal crystallite sizes by up to 20%. The ability to tune the metal content and crystalline domain size simultaneously makes GR-RLAL a potentially useful approach in the manufacturing of functional metal-LIPSS materials such as surface-enhanced Raman spectroscopy substrates.

Electron transport in chloroplasts: regulation and alternative pathways of electron transfer

This work represents an overview of electron transport regulation in chloroplasts as considered in the context of structure-function organization of photosynthetic apparatus in plants. A basic focus of the article is concentrated on a bifurcated oxidation of plastoquinol by the cytochrome b6f complex, which represents the rate-limiting step of electron transfer between photosystems 2 and 1. Electron transport along the chains of the noncyclic, cyclic and pseudocyclic electron flow, their relationships to generation of the trans-thylakoid difference in electrochemical potentials of protons in chloroplasts, and the pH-dependent mechanisms of regulation of the cytochrome b6f complex, are considered. Redox reactions with the participation of molecular oxygen and ascorbate, the alternative mediators of electron transport in chloroplasts, have also been discussed.

Vibrational Probe at the Electrochemical Interface: Dependence on Plasmon Coupling and Potential of the Lineshape in Two-Dimensional Infrared Spectroscopy.

Two-dimensional infrared spectroscopy of vibrational probes at an electrode surface shows promise for studying the structural dynamics at an active electrochemical interface. This interface is a complex environment where the solution structures in response to the applied potential. A strategy for achieving the necessary monolayer sensitivity is to use a plasmonically active electrode, which enhances the electromagnetic fields that produce the spectroscopic response. Here, we show how the coupling between the plasmon and the vibrations of the molecular monolayer impacts the FTIR and 2D IR spectroscopy, with an emphasis on the electrochemical potential difference spectra. We show how mixing between the vibrational and plasmonic states gives rise to the distortions that are observed in these measurements. This provides an important step toward 2D IR measurements of vibrational probes at the electrochemical interface as a tool for probing the structural dynamics in the double layer.

Electrometric and Electron Paramagnetic Resonance Measurements of a Difference in the Transmembrane Electrochemical Potential: Photosynthetic Subcellular Structures and Isolated Pigment-Protein Complexes.

A transmembrane difference in the electrochemical potentials of protons (ΔμH+) serves as a free energy intermediate in energy-transducing organelles of the living cell. The contributions of two components of the ΔμH+ (electrical, Δψ, and concentrational, ΔpH) to the overall ΔμH+ value depend on the nature and lipid composition of the energy-coupling membrane. In this review, we briefly consider several of the most common instrumental (electrometric and EPR) methods for numerical estimations of Δψ and ΔpH. In particular, the kinetics of the flash-induced electrometrical measurements of Δψ in bacterial chromatophores, isolated bacterial reaction centers, and Photosystems I and II of the oxygenic photosynthesis, as well as the use of pH-sensitive molecular indicators and kinetic data regarding pH-dependent electron transport in chloroplasts, have been reviewed. Further perspectives on the application of these methods to solve some fundamental and practical problems of membrane bioenergetics are discussed.

Electron Transport in Chloroplasts: Regulation and Alternative Pathways of Electron Transfer.

This work represents an overview of electron transport regulation in chloroplasts as considered in the context of structure-function organization of photosynthetic apparatus in plants. Main focus of the article is on bifurcated oxidation of plastoquinol by the cytochrome b6f complex, which represents the rate-limiting step of electron transfer between photosystems II and I. Electron transport along the chains of non-cyclic, cyclic, and pseudocyclic electron flow, their relationships to generation of the trans-thylakoid difference in electrochemical potentials of protons in chloroplasts, and pH-dependent mechanisms of regulation of the cytochrome b6f complex are considered. Redox reactions with participation of molecular oxygen and ascorbate, alternative mediators of electron transport in chloroplasts, have also been discussed.

Thorium Removal, Recovery and Recycling: A Membrane Challenge for Urban Mining.

Although only a slightly radioactive element, thorium is considered extremely toxic because its various species, which reach the environment, can constitute an important problem for the health of the population. The present paper aims to expand the possibilities of using membrane processes in the removal, recovery and recycling of thorium from industrial residues reaching municipal waste-processing platforms. The paper includes a short introduction on the interest shown in this element, a weak radioactive metal, followed by highlighting some common (domestic) uses. In a distinct but concise section, the bio-medical impact of thorium is presented. The classic technologies for obtaining thorium are concentrated in a single schema, and the speciation of thorium is presented with an emphasis on the formation of hydroxo-complexes and complexes with common organic reagents. The determination of thorium is highlighted on the basis of its radioactivity, but especially through methods that call for extraction followed by an established electrochemical, spectral or chromatographic method. Membrane processes are presented based on the electrochemical potential difference, including barro-membrane processes, electrodialysis, liquid membranes and hybrid processes. A separate sub-chapter is devoted to proposals and recommendations for the use of membranes in order to achieve some progress in urban mining for the valorization of thorium.

Using Ambient Pressure Photoelectron Spectroscopy to Investigate the Time Dependence of Electrostatic Potential Difference over the Interphase between an Electrode and an Electrolyte

Ambient pressure photoelectron spectroscopy (APPES) is a method well-suited for measuring the change ∆φ in electrostatic potential difference φ over an interphase between an electronic conductor and an insulator. APPES had previously been used to compare ∆φ over an interphase between an electrode and an electrolyte with the change in electrochemical potential difference ∆UWE-RE between the working and the reference electrode UWE-RE .[1] The relationship between ∆φ and ∆UWE-RE at low current-transient had been shown to follow two distinct trends depending on whether charge transfer of Li+ ions between an electrode and an electrolyte occurs or not.[1,2] In this work, APPES was used to investigate the time dependence of ∆φ after changing UWE-RE . The studied electrochemical system consisted of Au (working electrode), Li4Ti5O12 (reference electrode) and a second Li4Ti5O12 (counter electrode) with 0.008 M LiClO4 in propylene carbonate (PC) as the electrolyte. Pressure in the sample compartment was equal to the saturated PC pressure. APPES experiments were performed at HIPPIE beamline at MAX IV in Lund and were conducted as follows. After applying a potential step ∆UWE-RE , a C 1s spectrum was measured every 7 s. Incident photon energy was 1800 eV. Each spectrum was fitted using a Python code written especially for the obtained C 1s spectra. Time dependence of ∆φ was extracted from the shift in the kinetic energy ∆KE of the C=O peak (∆φ = ∆KE). Experiments were performed in both regimes, i.e. when the working electrode behaves as an ideal polarizable electrode and when it behaves as an ideal non-polarizable electrode, and have shown the time dependence of ∆φ to differ for the two regimes. Behaviour of ∆φ(t) as well as the experimental setup and spectral fitting using the Python code will be discussed.Figure 1: a) Schematic depiction of the electronic electrostatic potential φ between a working (WE) and a reference electrode (RE). Electrostatic potential profile is not to scale. b) An example of the experimentally obtained time dependence of the C=O peak kinetic energy KE(t). KE(t) is related to φ(t) as ∆φ(t) = ∆KE(t).

Cryptands on a Solid Support for the Separation of Europium from Gadolinium.

With the great demand for europium in green-energy technologies comes the need for innovative methods to isolate the elements. We introduce a solid-liquid extraction method using a 2.2.2-cryptand-modified solid support to separate europium from gadolinium using their differences in electrochemical potential. The method overcomes challenges associated with the separation of those two ions that have similar coordination chemistry in the +3 oxidation state. A competitive adsorption study in the cryptand system between EuII/EuIII and GdIII shows greater affinity for EuII relative to GdIII. After separation from GdIII, Eu was released by oxidizing EuII to EuIII with 99.3% purity. The purity of separated Eu is unaffected by pH between pH 3.0 and 5.5. Overall, we demonstrate that by modifying a solid support with 2.2.2-cryptand, divalent europium can be separated from trivalent gadolinium based on the differences of affinities of 2.2.2-cryptand for the two ions.

Deep cryogenic treatment of AA7050: tensile response and corrosion susceptibility

Cryogenic treatments represent an innovative technology developed with the aim of improving the performance of metallic alloys. The beneficial effects on steels are well documented in the literature, whereas their influence on other materials, such as aluminum alloys, is still not completely clarified. Even if the scientific literature reports conflicting data and conclusions, the industrial applications of such treatments are constantly growing. In the present experimental work, the mechanical and corrosion properties of a high-performance 7050 aluminum alloy plate were studied after cryogenic treatment at − 196 °C in liquid nitrogen. Tensile tests were performed on heat-treated samples, and intergranular corrosion tests were carried out on prismatic samples, according to ASTM G110-92 standard. The specimens were exposed to the corrosive environment and the effect of intergranular corrosion was measured by quantitative analysis using light-optical microscopy (LOM). Whereas trifling variation was observed in the mechanical resistance and plastic behavior, the corrosion tests showed a benefic effect of the cryogenic treatment. The microstructure was investigated by FEG-SEM analysis, revealing a different distribution of precipitates near the grain boundaries, which was able to reduce the electrochemical potential difference among these regions and the center-grain.

Coulombic Organization in Membrane-Embedded Rotary Motor of ATP Synthase.

The electrochemical potential difference of protons across the membrane is used to synthesize ATP through the proton-motive rotatory motion of the membrane-embedded region of ATP synthase called Fo. In this study, we illuminate the unsolved proton-motive rotary mechanism of Fo on the basis of atomistic simulation with full description of protein, lipid, and water molecules, and highlight the underlying Coulombic design. We first show that a water channel is spontaneously formed at the interfacial region between the rotor (c-ring) and the stator (a-subunit). The observed water channel is a full channel penetrating the membrane, but a Coulomb barrier by a strictly conserved arginine of the a-subunit dominates at the midpoint of the full channel, preventing proton leakage. Our molecular dynamics simulation further demonstrates that the Coulomb attraction between the arginine and the essential glutamic acid of the c-subunit drives the c-ring rotation. We finally illustrate that the charge-state changes of the glutamic acids, enabled by the electrochemical potential difference of proton and the thermal motion, can produce unidirectional rotation of the c-ring.

Electrochemical and Structural Study of the Buried Tryptophan in Azurin: Effects of Hydration and Polarity on the Redox Potential of W48.

Tryptophan serves as an important redox-active amino acid in mediating electron transfer and mitigating oxidative damage in proteins. We previously showed a difference in electrochemical potentials for two tryptophan residues in azurin with distinct hydrogen-bonding environments. Here, we test whether reducing the side chain bulk at position Phe110 to Leu, Ser, or Ala impacts the electrochemical potentials (E°) for tryptophan at position 48. X-ray diffraction confirmed the influx of crystallographically resolved water molecules for both the F110A and F110L tyrosine free azurin mutants. The local environments of W48 in all azurin mutants were further evaluated by UV resonance Raman (UVRR) spectroscopy to probe the impact of mutations on hydrogen bonding and polarity. A correlation between the frequency of the ω17 mode─considered a vibrational marker for hydrogen bonding─and E° is proposed. However, the trend is opposite to the expectation from a previous study on small molecules. Density functional theory calculations suggest that the ω17 mode reflects hydrogen bonding as well as local polarity. Further, the UVRR data reveal different intensity/frequency shifts of the ω9/ω10 vibrational modes that characterize the local H-bonding environments of tryptophan. The cumulative data support that the presence of water increases E° and reveal properties of the protein microenvironment surrounding tryptophan.