Researcher:
Dikbaş, Uğur Meriç

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Master Student

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Uğur Meriç

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Dikbaş

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Dikbaş, Uğur Meriç

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2016 - 201972020 - 20213

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    Identification and characterization of a new class of (6−4) photolyase from Vibrio cholerae
    (Amer Chemical Soc, 2019) Ozcelik, Gozde; Ozturk, Nuri; N/A; N/A; Department of Chemical and Biological Engineering; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Dikbaş, Uğur Meriç; Tardu, Mehmet; Gül, Şeref; Barış, İbrahim; Kavaklı, İbrahim Halil; Master Student; PhD Student; Researcher; Teaching Faculty; Faculty Member; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; College of Engineering; N/A; N/A; N/A; 111629; 40319
    Light is crucial for many biological activities of most organisms, including vision, resetting of circadian rhythm, photosynthesis, and DNA repair. The cryptochrome/photolyase family (CPF) represents an ancient group of UV-A/blue light sensitive proteins that perform different functions such as DNA repair, circadian photoreception, and transcriptional regulation. The CPF is widely distributed throughout all organisms, including marine prokaryotes. The bacterium Vibrio cholerae was previously shown to have a CPD photolyase that repairs UV-induced thymine dimers and two CRY-DASHs that repair UV-induced single-stranded DNA damage. Here, we characterize a hypothetical gene Vca0809 encoding a new member of CPF in this organism. The spectroscopic analysis of the purified protein indicated that this enzyme possessed a catalytic cofactor, FAD, and photoantenna chromophore 6,7-dimethyl 8-ribityllumazin. With a slot blot-based DNA repair assay, we showed that it possessed (6-4) photolyase activity. Further phylogenetic and computational analyses enabled us to classify this gene as a member of the family of iron-sulfur bacterial cryptochromes and photolyases (FeS-BCP). Therefore, we named this gene Vc(6-4) FeS-BCP.
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    Glu-370 in the large subunit influences the substrate binding, allosteric, and heat stability properties of potato ADP-glucose pyrophosphorylase
    (Elsevier Ireland Ltd, 2016) Çalışkan, Mahmut; Cevahir, Gül; N/A; Department of Chemical and Biological Engineering; N/A; Department of Molecular Biology and Genetics; N/A; Department of Chemical and Biological Engineering; Seferoğlu, Ayşe Bengisu; Gül, Şeref; Dikbaş, Uğur Meriç; Barış, İbrahim; Koper, Kaan; Kavaklı, İbrahim Halil; PhD Student; Researcher; Master Student; Teaching Faculty; Master Student; Faculty Member; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Sciences; Graduate School of Sciences and Engineering; College of Engineering; N/A; 289253; N/A; 111629; N/A; 40319
    ADP-glucose pyrophosphorylase (AGPase) is a key allosteric enzyme in plant starch biosynthesis. Plant AGPase is a heterotetrameric enzyme that consists of large (LS) and small subunits (SS), which are encoded by two different genes. In this study, we showed that the conversion of Glu to Gly at position 370 in the LS of AGPase alters the heterotetrameric stability along with the binding properties of substrate and effectors of the enzyme. Kinetic analyses revealed that the affinity of the (LSSSWT)-S-E370G AGPase for glucose 1-phosphate is 3-fold less than for wild type (WT) AGPase. Additionally, the (LSSSWT)-S-E370G AGPase requires 3-fold more 3-phosphogyceric acid to be activated. Finally, the LS(E370G)SS(WT)AGPase is less heat stable compared with the WT AGPase. Computational analysis of the mutant Gly-370 in the 3D modeled LS AGPase showed that this residue changes charge distribution of the surface and thus affect stability of the LS AGPase and overall heat stability of the heterotetrameric AGPase. In summary, our results show that LSE370 intricately modulate the heat stability and enzymatic activity of potato the AGPase.
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    RNA-seq analysis of the transcriptional response to blue and red light in the extremophilic red alga, Cyanidioschyzon merolae
    (Springer, 2016) N/A; N/A; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Tardu, Mehmet; Dikbaş, Uğur Meriç; Barış, İbrahim; Kavaklı, İbrahim Halil; PhD Student, Master Student; Teaching Faculty; Faculty Member; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; 256467; N/A; 111629; 40319
    Light is one of the main environmental cues that affects the physiology and behavior of many organisms. The effect of light on genome-wide transcriptional regulation has been well-studied in green algae and plants, but not in red algae. Cyanidioschyzon merolae is used as a model red algae, and is suitable for studies on transcriptomics because of its compact genome with a relatively small number of genes. In addition, complete genome sequences of the nucleus, mitochondrion, and chloroplast of this organism have been determined. Together, these attributes make C. merolae an ideal model organism to study the response to light stimuli at the transcriptional and the systems biology levels. Previous studies have shown that light significantly affects cell signaling in this organism, but there are no reports on its blue light- and red light-mediated transcriptional responses. We investigated the direct effects of blue and red light at the transcriptional level using RNA-seq. Blue and red lights were found to regulate 35 % of the total genes in C. merolae. Blue light affected the transcription of genes involved in protein synthesis while red light specifically regulated the transcription of genes involved in photosynthesis and DNA repair. Blue or red light regulated genes involved in carbon metabolism and pigment biosynthesis. Overall, our data showed that red and blue light regulate the majority of the cellular, cell division, and repair processes in C. merolae.
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    Effective neural photostimulation using indium-based type-ii quantum dots
    (American Chemical Society (ACS), 2018) Şahin, Mehmet; Ow-Yang, Cleva W.; N/A; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Department of Electrical and Electronics Engineering; Jalali, Houman Bahmani; Aria, Mohammad Mohammadi; Dikbaş, Uğur Meriç; Sadeghi, Sadra; Kumar, Baskaran Ganesh; Kavaklı, İbrahim Halil; Nizamoğlu, Sedat; PhD Student; PhD Student; Master Student; PhD Student; Other; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; N/A; N/A; 40319; 130295
    Light-induced stimulation of neurons via photoactive surfaces offers rich opportunities for the development of therapeutic methods and high-resolution retinal prosthetic devices. Quantum dots serve as an attractive building block for such surfaces, as they can be easily functionalized to match the biocompatibility and charge transport requirements of cell stimulation. Although indium based colloidal quantum dots with type-I band alignment have attracted significant attention as a nontoxic alternative to cadmium-based ones, little attention has been paid to their photovoltaic potential as type-II heterostructures. Herein, we demonstrate type-II indium phosphide/zinc oxide core/shell quantum dots that are incorporated into a photoelectrode structure for neural photostimulation. This induces a hyperpolarizing bioelectrical current that triggers the firing of a single neural cell at 4 mu W mm(-2), 26-fold lower than the ocular safety limit for continuous exposure to visible light. These findings show that nanomaterials can induce a biocompatible and effective biological junction and can introduce a route in the use of quantum dots in photoelectrode architectures for artificial retinal prostheses.
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    Perovskite-based optoelectronic biointerfaces for non-bias-assisted photostimulation of cells
    (Wiley, 2019) Cameron, Petra J.; Pering, Samuel R; N/A; Department of Electrical and Electronics Engineering; N/A; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Department of Electrical and Electronics Engineering; Aria, Mohammad Mohammadi; Srivastava, Shashi Bhushan; Şekerdağ, Emine; Dikbaş, Uğur Meriç; Sadeghi, Sadra; Özdemir, Yasemin Gürsoy; Kavaklı, İbrahim Halil; Nizamoğlu, Sedat; PhD Student; Researcher; Researcher; Master Student; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; School of Medicine; College of Engineering; College of Engineering; N/A; N/A; N/A; N/A; N/A; 170592; 40319; 130295
    Organohalide perovskites have attracted significant attention for efficient solar energy harvesting. They boost the photoelectrical conversion efficiency of the solution-processable solar cells because of having a nearly 100% internal quantum efficiency, operating in both narrow- and broadband spectral regimes, near-infrared sub-bandgap absorption, and high diffusion length. At the same time, these optoelectronic properties make it an ideal candidate for photostimulation of neurons. However, the biocompatibility of perovskite and its longevity in a cell medium constitute a major limitation to use it for biological interfaces. Here, high-level perovskite stability and biocompatibility are shown by forming hydrophobic perovskite microcrystals and encapsulating them within a polydimethylsiloxane layer. For effective and safe photostimulation of cells perovskite microcrystals are interfaced with poly(3-hexylthiophene-2,5-diyl) (P3HT) polymer for dissociation of the photogenerated charge carriers, which leads to non-bias-assisted cell stimulation. The results point out a new direction for the use of perovskite for photomedicine.
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    Plasmon-coupled photocapacitor neuromodulators
    (American Chemical Society (ACS), 2020) Ülgüt, Burak; Çetin, Arif E.; N/A; N/A; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Melikov, Rustamzhon; Srivastava, Shashi Bhushan; Karatüm, Onuralp; Doğru-Yüksel, Itır Bakış; Jalali, Houman Bahmani; Sadeghi, Sadra; Dikbaş, Uğur Meriç; Kavaklı, İbrahim Halil; Nizamoğlu, Sedat; PhD Student; Researcher; PhD Student; PhD Student; Master Student; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; N/A; 40319; 130295
    Efficient transduction of optical energy to bioelectrical stimuli is an important goal for effective communication with biological systems. For that, plasmonics has a significant potential via boosting the light-matter interactions. However, plasmonics has been primarily used for heat-induced cell stimulation due to membrane capacitance change (i.e., optocapacitance). Instead, here, we demonstrate that plasmonic coupling to photocapacitor biointerfaces improves safe and efficacious neuromodulating displacement charges for an average of 185% in the entire visible spectrum while maintaining the faradic currents below 1%. Hot-electron injection dominantly leads the enhancement of displacement current in the blue spectral window, and the nanoantenna effect is mainly responsible for the improvement in the red spectral region. The plasmonic photocapacitor facilitates wireless modulation of single cells at three orders of magnitude below the maximum retinal intensity levels, corresponding to one of the most sensitive optoelectronic neural interfaces. This study introduces a new way of using plasmonics for safe and effective photostimulation of neurons and paves the way toward ultrasensitive plasmon-assisted neurostimulation devices.
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    PublicationOpen Access
    Biocompatible quantum funnels for neural photostimulation
    (American Chemical Society (ACS), 2019) N/A; Department of Chemical and Biological Engineering; N/A; Department of Electrical and Electronics Engineering; Department of Molecular Biology and Genetics; N/A; Jalali, Houman Bahmani; Doğru-Yüksel, Itır Bakış; Eren, Güncem Özgün; Nizamoğlu, Sedat; Karatüm, Onuralp; Melikov, Rustamzhon; Dikbaş, Uğur Meriç; Kavaklı, İbrahim Halil; Sadeghi, Sadra; Yıldız, Erdost; Ergün, Çağla; Şahin, Afsun; PhD Student; Faculty Member; PhD Student; Master Student; Faculty Member; PhD Student; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Department of Electrical and Electronics Engineering; Department of Molecular Biology and Genetics; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; School of Medicine; N/A; N/A; N/A; 130295; N/A; N/A; N/A; 40319; N/A; N/A; N/A; 171267
    Neural photostimulation has high potential to understand the working principles of complex neural networks and develop novel therapeutic methods for neurological disorders. A key issue in the light-induced cell stimulation is the efficient conversion of light to bioelectrical stimuli. In photosynthetic systems developed in millions of years by nature, the absorbed energy by the photoabsorbers is transported via nonradiative energy transfer to the reaction centers. Inspired by these systems, neural interfaces based on biocompatible quantum funnels are developed that direct the photogenerated charge carriers toward the bionanojunction for effective photostimulation. Funnels are constructed with indium-based rainbow quantum dots that are assembled in a graded energy profile. Implementation of a quantum funnel enhances the generated photoelectrochemical current 215% per unit absorbance in comparison with ungraded energy profile in a wireless and free-standing mode and facilitates optical neuromodulation of a single cell. This study indicates that the control of charge transport at nanoscale can lead to unconventional and effective neural interfaces.
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    PublicationOpen Access
    Bidirectional optical neuromodulation using capacitive charge-transfer
    (The Optical Society (OSA) Publishing, 2020) Department of Electrical and Electronics Engineering; N/A; Department of Chemical and Biological Engineering; Department of Molecular Biology and Genetics; Melikov, Rustamzhon; Srivastava, Shashi Bhushan; Karatüm, Onuralp; Nizamoğlu, Sedat; Doğru-Yüksel, Itır Bakış; Dikbaş, Uğur Meriç; Kavaklı, İbrahim Halil; PhD Student; Researcher; PhD Student; Faculty Member; Master Student; Faculty Member; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Department of Molecular Biology and Genetics; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; N/A; N/A; N/A; 130295; N/A; N/A; 40319
    Artificial control of neural activity allows for understanding complex neural networks and improving therapy of neurological disorders. Here, we demonstrate that utilization of photovoltaic biointerfaces combined with light waveform shaping can generate safe capacitive currents for bidirectional modulation of neurons. The differential photoresponse of the biointerface due to double layer capacitance facilitates the direction control of capacitive currents depending on the slope of light intensity. Moreover, the strength of capacitive currents is controlled by changing the rise and fall time slope of light intensity. This approach allows for high-level control of the hyperpolarization and depolarization of membrane potential at single-cell level. Our results pave the way toward advanced bioelectronic functionalities for wireless and safe control of neural activity.
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    PublicationOpen Access
    Bulk-heterojunction photocapacitors with high open-circuit voltage for low light intensity photostimulation of neurons
    (Royal Society of Chemistry (RSC), 2021) Department of Electrical and Electronics Engineering; Department of Molecular Biology and Genetics; N/A; Department of Chemical and Biological Engineering; N/A; Srivastava, Shashi Bhushan; Melikov, Rustamzhon; Yıldız, Erdost; Dikbaş, Uğur Meriç; Sadeghi, Sadra; Kavaklı, İbrahim Halil; Şahin, Afsun; Nizamoğlu, Sedat; Researcher; PhD Student; PhD Student; Master Student; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; School of Medicine; N/A; N/A; N/A; N/A; N/A; 40319; 171267; 130295
    High-level transduction control of light to bioelectricity is an important goal for the realization of superior neuron-device interfaces that can be used for regulating fundamental cellular processes to cure neurological disorders. In this study, a single-junction, wireless, and capacitive-charge-injecting optoelectronic biointerface with negligible faradaic reactions by using a high open-circuit voltage (0.75 V) bulk heterojunction of PTB7-Th:PC71BM is designed and demonstrated. The biointerface generates a 2-fold higher photocurrent in comparison with P3HT:PC61BM having an open-circuit voltage of 0.55 V. Furthermore, we observed that light intensity is logarithmically correlated with the open-circuit voltage of solar cells, and the photovoltage of the biointerfaces varies the switching speed of capacitive charge-transfer. Finally, pulse trains of capacitive stimuli at a low light intensity of 20 mW cm−2elicit action potential generation in primary hippocampal neurons extracted from E15-E17 Wistar Albino rats. These findings show the great promise of high open-circuit voltage bulk heterojunction biointerfaces for non-genetic, all-optical and safe modulation of neurons.
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    PublicationOpen Access
    Band alignment engineers faradaic and capacitive photostimulation of neurons without surface modification
    (American Physical Society (APS), 2019) Department of Electrical and Electronics Engineering; N/A; Department of Chemical and Biological Engineering; Department of Molecular Biology and Genetics; Srivastava, Shashi Bhushan; Melikov, Rustamzhon; Aria, Mohammad Mohammadi; Dikbaş, Uğur Meriç; Kavaklı, İbrahim Halil; Nizamoğlu, Sedat; Researcher; PhD Student; Master Student; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Department of Molecular Biology and Genetics; College of Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; N/A; 40319; 130295
    Photovoltaic substrates have attracted significant attention for neural photostimulation. The control of the Faradaic and capacitive (non-Faradaic) charge transfer mechanisms by these substrates are critical for safe and effective neural photostimulation. We demonstrate that the intermediate layer can directly control the strength of the capacitive and Faradaic processes under physiological conditions. To resolve the Faradaic and capacitive stimulations, we enhance photogenerated charge density levels by incorporating PbS quantum dots into a poly(3-hexylthiophene-2,5-diyl):([6,6]-Phenyl-C61-butyric acid methyl ester (P3HT:PCBM) blend. This enhancement stems from the simultaneous increase of absorption, well matched band alignment of PbS quantum dots with P3HT:PCBM, and smaller intermixed phase-separated domains with better homogeneity and roughness of the blend. These improvements lead to the photostimulation of neurons at a low light intensity level of 1 mW cm(-2), which is within the retinal irradiance level. These findings open up an alternative approach toward superior neural prosthesis.