Au@Pd nanozyme-mediated catalytic therapy: a novel strategy for targeting tumor microenvironment in cancer treatment.

BACKGROUND: Breast cancer, with its high morbidity and mortality rates, is a significant global health burden. Traditional treatments-surgery, chemotherapy, and radiotherapy-are widely used but come with drawbacks such as recurrence, metastasis, and significant side effects, including damage to healthy tissues. To address these limitations, new therapeutic strategies are being developed. Peroxidases (POD) can catalyze excess H2O2 in the tumor microenvironment to generate reactive oxygen species (ROS), which induce cancer cell apoptosis by disrupting redox homeostasis and modulating apoptosis-related proteins. However, natural enzymes face challenges like poor stability, high cost, and sensitivity to environmental conditions, limiting their application in breast cancer treatment. Nanozymes, nanomaterials with enzyme-like activity, offer a promising alternative by overcoming these limitations. METHODS: In this study, we successfully prepared Au@Pd nanozymes with peroxidase activity by depositing metallic Pd on Au nanoparticles (Au NPs) synthesized using a trisodium citrate reduction method and ascorbic acid reduction. The in vitro validation was conducted through a series of experiments, including ROS detection, flow cytometry, CCK-8 assay, DNA damage assessment, live/dead cell staining, Western blot (WB), and qPCR. Tumor treatment was performed via tail vein injection of the drug, followed by HE staining of the treated tissues and biochemical analysis of the blood. RESULTS: Au@Pd nanozymes can effectively accumulate at the tumor site through the EPR effect and exert peroxidase-like activity, catalyzing the excess H2O2 in the tumor microenvironment to produce ROS. This triggers apoptosis pathways and DNA damage, leading to the downregulation of the anti-apoptotic protein Bcl-2, upregulation of the pro-apoptotic protein Bax, and induction of apoptosis-related genes, demonstrating strong anti-tumor effects. CONCLUSIONS: This study developed an efficient nanozyme-mediated catalytic therapy strategy targeting the tumor microenvironment for the treatment of breast cancer cells.

Nanomotors as Therapeutic Agents: Advancing Treatment Strategies for Inflammation-Related Diseases.

Inflammation is a physiological response of the body to harmful stimuli such as pathogens, damaged cells, or irritants, involving a series of cellular and molecular events. It is associated with various diseases including neurodegenerative disorders, cancer, and atherosclerosis, and is a leading cause of global mortality. Key inflammatory factors, such as Tumor Necrosis Factor-alpha (TNF-α), Interleukin-1 (IL-1), Interleukin-6 (IL-6), Monocyte Chemoattractant Protein-1 (MCP-1/CCL2), RANTES (CCL5), and prostaglandins, play central roles in inflammation and disease progression. Traditional treatments such as NSAIDs, steroids, biologic agents, and antioxidants have limitations. Recent advancements in nanomaterials present promising solutions for treating inflammation-related diseases. Unlike nanomaterials that rely on passive targeting and face challenges in precise drug delivery, nanomotors, driven by chemical or optical stimuli, offer a more dynamic approach by actively navigating to inflammation sites, thereby enhancing drug delivery efficiency and therapeutic outcomes. Nanomotors allow for controlled drug release in response to specific environmental changes, such as pH and inflammatory factors, ensuring effective drug concentrations at disease sites. This active targeting capability enables the use of smaller drug doses, which reduces overall drug usage, costs, and potential side effects compared to traditional treatments. By improving precision and efficiency, nanomotors address the limitations of conventional therapies and represent a significant advancement in the treatment of inflammation-related diseases. This review summarizes the latest research on nanomotor-mediated treatment of inflammation-related diseases and discusses the challenges and future directions for optimizing their clinical translation.

Study on the mechanism of lupenone for treating type 2 diabetes by integrating pharmacological evaluation and network pharmacology.

CONTEXT: Lupenone (LUP) is the active ingredient of Musa basjoo Sieb. et Zucc. (Musaceae) with antidiabetes effects, but an unclear underlying mechanism of action. OBJECTIVE: Animal experiments combined with network pharmacology were used to explore the mechanism of LUP for treating diabetes. MATERIALS AND METHODS: Insulin resistance (IR) in male Sprague-Dawley rats with type 2 diabetic was induced using a high-fat diet and streptozotocin. The selected rats were divided into normal group, model group, positive group and LUP (2.0, 4.0 and 8.0 mg/kg) groups, and orally administrated twice daily with Tween 80, rosiglitazone or LUP. Fasting blood glucose (FBG), oxidative stress index, blood lipids and IR-related targets were detected. A network pharmacology analysis was performed. RESULTS: Compared to the model group, LUP (8.0 mg/kg) significantly decreased the levels of FBG (22.3%), LEP (9.5%), HbA1c (14.9%) and MDA (12.3%), increased the ADPN (24.2%) levels and GSH-PX activity (12.4%) (p < 0.05), improved oxidative stress, lipid metabolism disorders and pancreas pathological changes, increased the mRNA and protein expression of InsR (3.7-fold and 1.3-fold), IRS-1 (3-fold and 2-fold), IRS-2 (2-fold and 1.6-fold), GLUT-4 (2-fold and 2.4-fold) in skeletal muscle and IRS-1 (6-fold and 1.6-fold), IRS-2 (5.8-fold and 1.5-fold), GLUT-4 (2.5-fold and 1.7-fold) and PPAR-γ (7-fold and 1.4-fold) in adipose tissue (p < 0.05). Network pharmacology analysis revealed that LUP improves IR by multiple targets and signal pathways. CONCLUSIONS: The mechanism of LUP for treating diabetes is related to improving IR. LUP has the potential to be developed as a new drug for treating type 2 diabetes.

Evaluation of chemical similarity among rhizome, pseudo stem and leaf of Musa basjoo by UPLC-ELSD fingerprint combined with chemo metrics methods.

Rhizoma Musa (the Rhizome of Musa basjoo Sied.et Zucc.) is used as a traditional medical herb of Miao nationality in Guizhou province, in China. It has the efficacy of clearing heat and detoxifying, quenching thirst, diuresis, etc. Modern pharmacological studies have shown that it has hypoglycemic, inhibition of α-glucosidase, and anti-inflammatory activity. However, when the rhizomes of Musa basjoo are dug up, the rhizomes are unable regenerate, and the pseudostem and leaf are discarded, which not only pollutes the environment, but also causes a huge waste of herb resources. In this study, a UPLC-ELSD fingerprint analysis with chemometric method was applied for the evaluation of chemical similarity among rhizome, pseudostem and leaf of Musa Basjoo. The results indicated that the combined method could efficiently analyze and compare the chemical similarity among rhizome, pseudostem, and leaf of Musa Basjoo. The proposed method provides the foundation for the resource substitution of the rhizome, pseudostem, and leaf of Musa Basjoo.

MiR-342-3p inhibition promotes cell proliferation and invasion by directly targeting ID4 in pre-eclampsia.

AIM: This study aimed to explore the miR-342-3p expression in pre-eclampsia (PE) placentas and confirm whether miR-342-3p exerts effects on proliferation and migration of HTR-8/SVneo trophoblastic cells. METHODS: The PE placentas (n = 8) were taken from gravidas complicated by PE and delivered after 34 weeks. The chorionic plates and the basal plates were separately taken from the placenta disc near the position of umbilical cord insertion. RT-qPCR was used to measure the expression of miR-342-3p in the chorionic plates and the basal plates. Cell invasion assay and MMT assay were used to assess the effects of miR-342-3p on proliferation and migration of HTR-8/SVneo trophoblastic cells. Luciferase reporter assay and Western blotting were used to analyze the target of miR-342-3p and investigate the detailed mechanisms. RESULTS: The expression of miR-342-3p was upregulated in both basal plates and chorionic plates in patients with PE compared with healthy pregnant individuals. MiR-342-3p inhibitor suppressed the cell viability and invasion, and induced apoptosis in trophoblast cells. Furthermore, inhibitor of DNA binding (ID)-4 (ID4) was a direct target of miR-342-3p, and knockdown of ID4 abrogated the regulation effect of miR-342-3p on cell viability, apoptosis and invasion. CONCLUSION: Inhibition of miR-342-3p expression may suppress the occurrence of PE by targeting ID4 in vitro.

Evaluation of the Mandibular Lingual Canal and Anterior Loop Length to Minimize Complications Associated With Anterior Mandibular Surgeries: A Cone-Beam Computed Tomography Study.

PURPOSE: This retrospective study evaluated the localization, incidence, and dimensions of the mandibular lingual canal and the anterior loop in the Taiwanese population using the simulation and visual interpretation of cone-beam computed tomography to minimize complications during symphysis block surgical procedures. MATERIALS AND METHODS: The sample population consisted of 215 patients (105 men and 110 women; mean age, 57 yr). The median lingual canal, symphysis bone thickness, and anterior loop length were defined and calculated using cone-beam computed tomography and 3-dimensional reconstructed images. The correlation of all data for men and women was assessed and analyzed statistically using unpaired t tests. RESULTS: All patients exhibited at least 1 median lingual canal in the symphysis, and the diameter of the main branch ranged from 0.21 to 1.48 mm (mean, 0.85 mm), with relevant differences between genders (longer in men than in women). A harvesting depth of 4 mm for the distance from the buccal bone to the terminal end of the median lingual canal resulted in a risk of neurovascular injury (13.0%); this risk was notably higher in women (19.1%) than in men (6.7%). The right and left anterior loop lengths ranged from 0 to 5.46 mm (mean, 2.60 mm) and from 0 to 5.57 mm (mean, 2.61 mm), respectively, with no relevant differences between genders or sides. CONCLUSIONS: The results suggest that routine cone-beam computed tomographic examinations before surgical interventions in the symphysis region are necessary because of the numerous complicated anatomic variations.

Probing Electric Field Effect on Covalent Interactions at a Molecule-Semiconductor Interface.

Fundamental understanding of the energetic coupling properties of a molecule-semiconductor interface is of great importance. The changes in molecular conformations and vibrational modes can have significant impact on the interfacial charge transfer reactions. Here, we have probed the change in the interface properties of alizarin-TiO2 system as a result of the externally applied electric field using single-hot spot microscopic surface-enhanced Raman spectroscopy (SMSERS) and provided a theoretical understanding of our experimental results by density functional theory (DFT) calculations. The perturbation, caused by the external potential, has been observed as a shift and splitting of the 648 cm(-1) peak, typical indicator of the strong coupling between alizarin and TiO2, at SMSERS. On the basis of our experimental results and DFT calculations, we suggest that electric field has significant effects on vibrational coupling at the molecule-TiO2 interface. The presence of perturbed alizarin-TiO2 coupling under interfacial electric potential may lead to changes in the interfacial electron transfer dynamics. Additionally, heterogeneously distributed dye molecules at the interface on nanometer length scale and different chromophore-semiconductor binding interactions under charge accumulation associated interfacial electric field changes create intrinsically inhomogeneous interfacial ET dynamics associated with both static and dynamic disorders.

Population genetic structure and approximate Bayesian computation analyses reveal the southern origin and northward dispersal of the oriental fruit moth Grapholita molesta (Lepidoptera: Tortricidae) in its native range.

The oriental fruit moth (OFM) Grapholita molesta is one of the most destructive orchard pests. Assumed to be native to China, the moth is now distributed throughout the world. However, the evolutionary history of this moth in its native range remains unknown. In this study, we explored the population genetic structure, dispersal routes and demographic history of the OFM in China and South Korea based on mitochondrial genes and microsatellite loci. The Mantel test indicated a significant correlation between genetic distance and geographical distance in the populations. Bayesian analysis of population genetic structure (baps) identified four nested clusters, while the geneland analysis inferred five genetic groups with spatial discontinuities. Based on the approximate Bayesian computation approach, we found that the OFM was originated from southern China near the Shilin area of Yunnan Province. The early divergence and dispersal of this moth was dated to the Penultimate glaciation of Pleistocene. Further dispersal from southern to northern region of China occurred before the last glacial maximum, while the expansion of population size in the derived populations in northern region of China occurred after the last glacial maximum. Our results indicated that the current distribution and structure of the OFM were complicatedly influenced by climatic and geological events and human activities of cultivation and wide dissemination of peach in ancient China. We provide an example on revealing the origin and dispersal history of an agricultural pest insect in its native range as well as the underlying factors.

RP-HPLC characterization of lupenone and ß-sitosterol in rhizoma musae and evaluation of the anti-diabetic activity of lupenone in diabetic Sprague-Dawley rats.

With the aim of characterizing the active ingredients lupenone and ß-sitosterol in Rhizoma Musae samples a reversed-phase HPLC method for the separation of these two compounds in Rhizoma Musae samples was developed (regression coefficient>0.9996). The method was further applied to quantify lupenone and ß-sitosterol content in Rhizoma Musae samples cultured in different growth environments. Different variables such as geographical location, growth stage, and harvest time, demonstrated differential effects on lupenone and ß-sitosterol levels. Moreover, we determined the optimum conditions for cultivation and harvesting of Rhizoma Musae herbs. Lupenone administration caused a significant reduction in fasting blood glucose (FBG) levels in diabetic rats at doses of 1.78, 5.33, and 16.00 mg·kg⁻¹·day⁻¹ for 14 days, the glycated hemoglobin (HbA1c) levels of diabetic rats also significantly reduced at doses of 5.33, and 16.00 mg·kg⁻¹·day⁻¹, indicating a robust antidiabetic activity. To our knowledge, this is the first report of an optimized HPLC method successfully applied to quantify lupenone and ß-sitosterol, and its applicability in optimizing Rhizoma Musae growth. Animal experiments also showed for the first time that lupenone from Rhizoma Musae has anti-diabetic activity.

Macrophage polarization: an important role in inflammatory diseases.

Macrophages are crucial cells in the human body's innate immunity and are engaged in a variety of non-inflammatory reactions. Macrophages can develop into two kinds when stimulated by distinct internal environments: pro-inflammatory M1-like macrophages and anti-inflammatory M2-type macrophages. During inflammation, the two kinds of macrophages are activated alternatively, and maintaining a reasonably steady ratio is critical for maintaining homeostasis in vivo. M1 macrophages can induce inflammation, but M2 macrophages suppress it. The imbalance between the two kinds of macrophages will have a significant impact on the illness process. As a result, there are an increasing number of research being conducted on relieving or curing illnesses by altering the amount of macrophages. This review summarizes the role of macrophage polarization in various inflammatory diseases, including autoimmune diseases (RA, EAE, MS, AIH, IBD, CD), allergic diseases (allergic rhinitis, allergic dermatitis, allergic asthma), atherosclerosis, obesity and type 2 diabetes, metabolic homeostasis, and the compounds or drugs that have been discovered or applied to the treatment of these diseases by targeting macrophage polarization.

Detection of muscular system adverse reaction signals in sacubitril/valsartan treatment combined with statins.

Objective: To detect muscular system adverse reaction signals of sacubitril/valsartan treatment combined with statins (atorvastatin, rosuvastatin, simvastatin) to provide a reference for clinical administration. Methods: Multiplicative and additive models were used to mine the FDA's spontaneous reports database to detect signals of drug-drug interactions between sacubitril/valsartan and statins. SAS 9.4 software was used to conduct statistical tests for suspicious signals to determine whether the signals were statistically significant. Results: A total of 8,883,870 adverse reaction reports were analyzed. The combinations "sacubitril/valsartan - simvastatin - musculoskeletal muscle pain" had statistically significant correlation signals in both models (P < 0.05). The combination "sacubitril/valsartan - atorvastatin - myopathy" and "sacubitril/valsartan-simvastatin - myopathy" had statistically significant correlation signal in the multiplicative model (P < 0.05). Conclusion: Compared with a single drug, coadministration of sacubitril/valsartan with atorvastatin may increase safety risks to myopathy, with simvastatin may increase safety risks to the musculoskeletal pain and myopathy, which should be closely monitored in clinical practice.

Recent Advances in Nanomaterial-Mediated Cell Death for Cancer Therapy.

Nanomedicine has shown great anticancer potential by disrupting redox homeostasis and increasing the levels of oxidative stress, but the therapeutic effect is limited by factors including the intrinsic self-protection mechanism of tumors. Cancer cell death can be induced by the exploration of different cell death mechanisms, such as apoptosis, pyroptosis, necroptosis, cuproptosis, and ferroptosis. The merging of nanotechnology with biomedicine has provided tremendous opportunities to construct cell death-based nanomedicine for innovative cancer therapy. Nanocarriers are not only used for the targeted delivery of cell death inducers, but also as therapeutic components to induce cell death to achieve efficient tumor treatment. This review focuses on seven cell death modalities mediated by nanomaterials, such as apoptosis, pyroptosis, necroptosis, ferroptosis, cuprotosis, immunogenic cell death, and autophagy. The mechanisms of these seven cell death modalities are described in detail, as well as the preparation of nanomaterials that induce them and the mechanisms, they used to exert their effects. Finally, this work describes the potential future development based on the current knowledge related to cell death induced by nanomaterials.

Spatiotemporal decoupling between impervious surface areas and ecosystem services.

Impervious surface area, due to its high energy storage and low permeability, hinders the cycles of material and energy between soil and atmosphere, thus affecting the sustainable supply of ecosystem services. It is of great practical significance to explore the influence of impervious surface areas on ecosystem services for territorial spatial planning and ecological construction projects. Correlation analysis and decoupling are used to explore the spatiotemporal variation and interaction between impervious surface areas and six ecosystem services in Hangzhou Bay from 1996 to 2018. The results show that different abundance levels of impervious surface areas are negatively correlated with ecosystem services, and with the increase of the impervious surface areas, the correlation coefficients with ecosystem services gradually decrease; there are mostly weak decoupling (79.2%) and strong decoupling (11.9%) between impervious surface areas and ecosystem services from 2007 to 2018, and the central areas that have achieved urbanization are mostly dominated by strong and weak decoupling, while the peripheral areas of the central cities are dominated by expansive recoupling and expansive connection. These results indicate that the loss of ecosystem services can be mitigated with the continuous advancement of urbanization and the enhancement of land use intensification. Finally, based on the aforementioned results, differentiated control suggestions are proposed, in order to provide insights for the sustainability of the urbanization of Hangzhou Bay and other cities with similar characteristics around the world.

Single-cell imaging and spectroscopic analyses of Cr(VI) reduction on the surface of bacterial cells.

We investigate the single-cell reduction of toxic Cr(VI) by the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 (MR-1), an important bioremediation process, using Raman spectroscopy and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX). Our experiments indicate that the toxic, highly soluble Cr(VI) can be efficiently reduced to less toxic, nonsoluble Cr(2)O(3) nanoparticles by MR-1. Cr(2)O(3) is observed to emerge as nanoparticles adsorbed on the cell surface and its chemical nature is identified by EDX imaging and Raman spectroscopy. Co-localization of Cr(2)O(3) and cytochromes by EDX imaging and Raman spectroscopy suggests a terminal reductase role for MR-1 surface-exposed cytochromes MtrC and OmcA. Our experiments revealed that the cooperation of surface proteins OmcA and MtrC makes the reduction reaction most efficient, and the sequence of the reducing reactivity of MR-1 is wild type > single mutant ΔmtrC or mutant ΔomcA > double mutant (ΔomcA-ΔmtrC). Moreover, our results also suggest that direct microbial Cr(VI) reduction and Fe(II) (hematite)-mediated Cr(VI) reduction mechanisms may coexist in the reduction processes.

The water-energy-food nexus: a systematic bibliometric analysis.

Adequate water, electricity, and food are essential for sustainable development. Regional conflicts intensified by global water, energy, and food shortages necessitate a rethinking of the security and interdependence of these resources. However, most earlier scholars concentrated on the subsystems of the water-energy-food nexus (WEF nexus), lacking holistic studies. Therefore, to understand the history and current state of research on the WEF nexus and predict future research directions, this study analyzed 1313 journal articles from the Web of Science database between 2007 and 2022 using the bibliometric analysis and Citespace software. The findings in this study indicate that (1) the progress of the WEF nexus research can be classified into three stages between 2007 and 2022: the early stage (2007-2010), the fast-developing stage (2011-2015), and the steady and in-depth stage (2016-2022). The WEF nexus has become a hot zone for academic research. (2) Map of the network of countries, institutions, and author collaborations implies tight academic collaboration among countries, institutions, and writers. (3) Climate change, integrated WEF nexus, sustainable development, and security are research hotspots in this field. Meanwhile, energy security, circular economy, and resource allocation are advanced subjects in this field. These key findings can provide managers and researchers with valuable information for decision-making.

Lipopolysaccharide-pretreated plasmacytoid dendritic cells ameliorate experimental chronic kidney disease.

Plasmacytoid dendritic cells play important roles in inducing immune tolerance, preventing allograft rejection, and regulating immune responses in both autoimmune disease and graft-versus-host disease. In order to evaluate a possible protective effect of plasmacytoid dendritic cells against renal inflammation and injury, we purified these cells from mouse spleens and adoptively transferred lipopolysaccharide (LPS)-treated cells, modified ex vivo, into mice with adriamycin nephropathy. These LPS-treated cells localized to the kidney cortex and the lymph nodes draining the kidney, and protected the kidney from injury during adriamycin nephropathy. Glomerulosclerosis, tubular atrophy, interstitial expansion, proteinuria, and creatinine clearance were significantly reduced in mice with adriamycin nephropathy subsequently treated with LPS-activated plasmacytoid dendritic cells as compared to the kidney injury in mice given naive plasmacytoid dendritic cells. In addition, LPS-pretreated cells, but not naive plasmacytoid dendritic cells, convert CD4+CD25- T cells into Foxp3+ regulatory T cells and suppress the proinflammatory cytokine production of endogenous renal macrophages. This may explain their ability to protect against renal injury in adriamycin nephropathy.

Simultaneous spectroscopic and topographic near-field imaging of TiO2 single surface states and interfacial electronic coupling.

We have probed single surface states and the involved interfacial charge transfer coupling on the TiO(2) surface using confocal as well as tip-enhanced near-field topographic-spectroscopic imaging analysis on a niobium-doped rutile TiO(2)(110) surface. The confocal images excited with a radially polarized donut mode render ring-shaped excitation patterns typical for quantum systems with two perpendicular transition dipole moments. The tip-enhanced near-field optical images of single surface states are visualized by the strong exciton plasmon-polariton coupling localized at the subdomain boundaries with a spatial resolution of ∼15 nm (far beyond the optical diffraction limit). We suggest that the abundant surface states in the doped TiO(2) generate excitons under laser excitation which are strongly coupled to the surface plasmon-polaritons of the Au tip. Moreover, the interfacial electronic molecule-substrate coupling has been characterized by probing the molecule-perturbed surface states distribution and the associated specific Raman vibrational modes. The imaging and characterization of the surface states and their distributions on TiO(2) surfaces at nanoscale are critically relevant to a deep understanding of interfacial electron transfer dynamics and energetics involving in solar energy conversion, photocatalysis, and mechanistic understanding of surface-enhanced Raman scattering spectroscopy.

Probing ground-state single-electron self-exchange across a molecule-metal interface.

We have probed single-molecule redox reaction dynamics of hemin (chloride) adsorbed on Ag nanoparticle surfaces by single-molecule surface-enhanced Raman spectroscopy (SMSERS) combined with spectroelectrochemistry. Redox reaction at the molecule/Ag interface is identified and probed by the prominent fluctuations of the Raman frequency of a specific vibrational mode, ν(4), which is a typical marker of the redox state of the iron center in a hemin molecule. On the basis of the autocorrelation and cross-correlation analysis of the single-molecule Raman spectral trajectories and the control measurements of single-molecule spectroelectochemistry and electrochemical STM, we suggest that the single-molecule redox reaction dynamics at the hemin-Ag interface is primarily driven by thermal fluctuations. The spontaneous fluctuation dynamics of the single-molecule redox reaction is measured under no external electric potential across the molecule-metal interfaces, which provides a novel and unique approach to characterize the interfacial electron transfer at the molecule-metal interfaces. Our demonstrated approaches are powerful for obtaining molecular coupling and dynamics involved in interfacial electron transfer processes. The new information obtained is critical for a further understanding, design, and manipulation of the charge transfer processes at the molecule-metal interface or metal-molecule-metal junctions, which are fundamental elements in single-molecule electronics, catalysis, and solar energy conversion.

Extracellular reduction of hexavalent chromium by cytochromes MtrC and OmcA of Shewanella oneidensis MR-1.

To characterize the roles of cytochromes MtrC and OmcA of Shewanella oneidensis MR-1 in Cr(VI) reduction, the effects of deleting the mtrC and/or omcA gene on Cr(VI) reduction and the cellular locations of reduced Cr(III) precipitates were investigated. Compared to the rate of reduction of Cr(VI) by the wild type (wt), the deletion of mtrC decreased the initial rate of Cr(VI) reduction by 43.5%, while the deletion of omcA or both mtrC and omcA lowered the rate by 53.4% and 68.9%, respectively. In wt cells, Cr(III) precipitates were detected by transmission electron microscopy in the extracellular matrix between the cells, in association with the outer membrane, and inside the cytoplasm. No extracellular matrix-associated Cr(III) precipitates, however, were found in the cytochrome mutant cell suspension. In mutant cells without either MtrC or OmcA, most Cr(III) precipitates were found in association with the outer membrane, while in mutant cells lacking both MtrC and OmcA, most Cr(III) precipitates were found inside the cytoplasm. Cr(III) precipitates were also detected by scanning election microscopy on the surfaces of the wt and mutants without MtrC or OmcA but not on the mutant cells lacking both MtrC and OmcA, demonstrating that the deletion of mtrC and omcA diminishes the extracellular formation of Cr(III) precipitates. Furthermore, purified MtrC and OmcA reduced Cr(VI) with apparent k(cat) values of 1.2 ± 0.2 (mean ± standard deviation) and 10.2 ± 1 s(-1) and K(m) values of 34.1 ± 4.5 and 41.3 ± 7.9 µM, respectively. Together, these results consistently demonstrate that MtrC and OmcA are the terminal reductases used by S. oneidensis MR-1 for extracellular Cr(VI) reduction where OmcA is a predominant Cr(VI) reductase.

Interfacial electron transfer energetics studied by high spatial resolution tip-enhanced Raman spectroscopic imaging.

Interfacial electron transfer (ET) in TiO2-based systems is important in artificial solar energy harvesting systems, catalysis, and in advanced oxidative waste water treatment. The fundamental importance of ET processes and impending applications make the study of interfacial ET a promising research area. Photoexcitation of dye molecules adsorbed on the surface of wide band gap semiconductors, such as TiO2, results in the injection of electrons from the dye molecules to the conduction band of the semiconductor or energetically accessible surface electronic states. Using Raman spectroscopy and ensemble-averaging approaches,t he chemical bonding and vibrational relaxation of the ET processes have been extensively studied. However, due to the complexity of the interfacial ET energetics and dynamics, significant questions remain on characterizing the source of the observed complexities. To address these important issues, we have applied advanced spectroscopic and imaging techniques such as confocal and tip-enhanced near-field Raman as well as photoluminescence spectroscopic and topographic imaging. Here we explore single surface states on TiO2 as well as the interfacial electronic coupling of alizarin to TiO2 single crystalline surfaces.