Chemistry / Kimya
Permanent URI for this collectionhttps://hdl.handle.net/11147/4072
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Article Citation - WoS: 3Citation - Scopus: 4Lipid Bilayer on Wrinkled-Interfaced Graphene Field Effect Transistor(Elsevier Ltd., 2021) Özkendir İnanç, Dilce; Çelebi, Cem; Yıldız, Ümit HakanThis study describes lipid bilayer-based sensor interface on SiO2 encapsulated graphene field effect transistors (GFET). The SiO2 layer was utilized as a lipid compatible surface that drives bilayer formation. The two types of surface morphologies i) wrinkled morphology by thermal evaporation (TE) and ii) flat morphology by pulsed electron deposition (PED) were obtained. The sensing performance of wrinkled and flat interfaced-GFETs were investigated, pH sensitivity of wrinkled interfaced-GFETs were found to be ten fold larger than the flat ones. The enhanced sensitivity is attributed to thinning of the oxide layer by formation of wrinkles thereby facilitating electrostatic gating on graphene. We foresee that described wrinkled SiO2 interfaced-GFET holds promise as a cell membrane mimicking sensing platform for novel bioelectronic applications. © 2020Article Citation - WoS: 6Citation - Scopus: 7Development of a Water-Soluble 3-Formylbodipy Dye for Fluorogenic Sensing and Cell Imaging of Sulfur Dioxide Derivatives(Elsevier Ltd., 2019) Işık, Murat; Şimşek Turan, İlke; Dartar, SuayA new water-soluble, highly fluorogenic 3-formylBODIPY dye that enables the sensing of SO2 derivatives in aqueous buffers and cancer cells is reported. The quaternary ammonium group appended through the mesa-position of the BODIPY dye ensures water solubility. The probe exhibits high specificity for cytosolic (bi)sulfites and fluoresces brightly in human lung adenocarcinoma cells (A549). (C) 2019 Elsevier Ltd. All rights reserved.Article Citation - WoS: 6Citation - Scopus: 6Palladium-Catalyzed Coupling of 2-En Carbonates With Terminal Alkynes(Elsevier Ltd., 2018) Taç, Doğan; Artok, LeventThe first palladium-catalysed coupling of the carbonates of (E)-configured conjugated enynols with terminal alkynes is described. This method allows the synthesis of vinyl-allenynes with good yields. It has been determined that the method is not suitable for the (Z)-configured substrates.Article Citation - WoS: 4Citation - Scopus: 4Gas-Phase Structures and Proton Affinities of N-Terminal Proline Containing B2 + Ions From Protonated Model Peptides(Elsevier Ltd., 2015) Karaca, Sıla; Atik, Ahmet Emin; Elmacı, Nuran; Yalçın, TalatIn this study, we investigated the effect of the second amino acid identity of hexapeptides on gas-phase structures and the proton affinities of N-terminal proline containing b2 + ions produced from the fragmentation of b6 + ions under low-energy collision-induced dissociation (CID) tandem mass spectrometry (MS/MS). It should be noted that, among all other fragments, the b2 + and nominally b4 + (AAAA) ions ([M+H]+ → b6 + → b2 + (PX+) + b4 + (AAAA+) were mainly considered in this study. This is a unique example of consecutive cleavage of b6 + ions which fragments to b2 + and nominal b4 + ions. All structural and proton affinity calculations for b2 + ions were carried out with the B3LYP/6-31+G(d,p) level of theory. The study utilized C-terminal amidated model peptides consisting of PAAAAA-NH2 and PXAAAA-NH2 where X is phenylalanine (F), glutamic acid (E), tryptophan (W), and histidine (H) residue. Two main structural isomers of b2 + ions, namely oxazolone and diketopiperazine, have been considered for the computations. The results demonstrated that the proton affinities of oxazolone isomers of PX are greater than its diketopiperazine isomers. Higher correlation coefficient is calculated if the structure of PX is considered as oxazolone rather than diketopiperazine isomer. Additionally, a linear fit is observed between intensity ratio (PX/AAAA) and calculated proton affinities of PX ions. Additionally, MS/MS results revealed that the relative intensities of b2 +-PA, PF, and PE- ions are lower compared to the relative intensity of AAAA fragment ion. In contrast, b2 +-PW and PH- ions have higher relative intensities compared to the AAAA ion. This behavior is explained by the proton affinities of fragment ions computationally.Article Citation - WoS: 9Citation - Scopus: 9The Role of Lysine ?-Amine Group on the Macrocyclization of B Ions(Elsevier Ltd., 2012) Atik, Ahmet Emin; Görgülü, Güvenç; Yalçın, TalatA study was carried out to examine if the amine (NH 2) group located on the side chains of lysine (K), glutamine (Q), or asparagine (N) residue has any effect on the macrocyclization of b ions even though the N-terminals of the peptides were acetylated. The work utilized the model peptides Ac-KYAGFLVG, Ac-QYAGFLV-NH 2, and Ac-NYAGFLV-NH 2. The CID mass spectra of b 7 ions originated from these three peptides exhibited that the macrocyclization still occurred for the lysine containing peptide in spite of the N-terminal of the peptide was acetylated, but was failed to be observed for glutamine and asparagine containing peptides. These current results reveal that the lysine side chain ε-amine group has been involved in the macrocyclization of the peptide b ions for the N-terminal acetylated peptides and consequently, non-direct sequence b ions were observed in the CID mass spectra. However, due to the amide group on the side chains of the glutamine and asparagine residues, the nucleophilicity of their groups greatly reduced; therefore the scrambling b ions were not detected in their b 7 ion CID mass spectra. In addition, the effect of the lysine position was also studied for series of six isomeric octapeptides such as, Ac-KYAGFLVG, Ac-YKAGFLVG, Ac-YAKGFLVG, Ac-YAGKFLVG, Ac-YAGFKLVG and Ac-YAGFLKVG in order to examine the relationship between the intensities of non-direct sequence b ions and the lysine position in the octapeptide series. The results clearly demonstrated that the most abundant non-direct sequence b ions were observed for the first position of lysine residue in the N-terminal acetylated octapeptide, however, when the lysine residue gets closer to the C-terminal position the relative intensities of the scrambled b ions were greatly decreased.Article Citation - WoS: 7Citation - Scopus: 7Investigation of Peptide Size, Residue Position, Neighbor Amino Acid and Side Chain Effect on Macrocyclization of B N (n = 5-7) Ions(Elsevier Ltd., 2012) Taşoğlu, Çağdaş; Görgülü, Güvenç; Yalçın, TalatA systematic study was carried out to examine the effects of the side chain, peptide size, residue position, and neighboring amino acid on the macrocyclization of b ions. The work utilized isomeric model peptides YAGFLV-NH 2, AGFLVY-NH 2, GFLVYA-NH 2, FLVYAG-NH 2, LVYAGF-NH 2, VYAGFL-NH 2, which all have the same amino acid sequence in cyclic form. The b 6 ions derived from all these isomeric peptides form the same macrocyclic structure due to the generation of the same amino acid sequence order upon cyclization. Hence, the MS/MS spectra and breakdown graphs of b 6 ions derived from these peptides are similar to each other. However, the relative intensities of the non-direct sequence ions in both the MS/MS spectra and breakdown graphs of the b 6 ions derived from FAYVGL-NH 2, GVYALF-NH 2 and VFYLAG-NH 2 show a different distribution from each other and the first series, even though they are all isomeric peptides. This could be due to the different amino acid sequence order in the cyclic forms of these peptides. It is clearly shown that the neighboring amino acid influences the selective opening of the macrocyclic form. Additionally, XYAGFLV-NH 2 and YAGXFLV-NH 2 (where X = C, D, E, H, K, M, N, P, Q, S, T, and W are amino acid residues) were also studied in order to examine the influence of the peptide size, amino acid side chain, and position on the ring formation and cleavage of macrocyclic b 5, b 6 and b 7 ions. The results have clearly shown that b 6 and b 7 ions have a higher tendency of macrocyclization compared to b 5 ions with the exception of QYAGFLV-NH 2. Additionally, it was observed that selective ring opening is also dependent on the size of the b ions and the position of the amino acid residue. From our study of the macrocyclic b 6 ions of our model peptides, the Q, W, K, and M residues were found to be more favorable eliminations when compared to C, D, E, H, N, P, S, and T. Based on the results, no preferential cleavage order can be specified depending on the nature of amino acid side chain.Article Citation - WoS: 7Citation - Scopus: 7Cleavage of Ring a and Formation of an Unusual Nor-Triterpene Skeleton Via the Baeyer-Villiger Reaction(Elsevier Ltd., 2012) Tağ, Özgür; Çağır, Ali; Khan, Ikhlas A.; Bedir, ErdalWith the aim to generate a compound library for our biological screening studies, cycloastragenol was subjected to chemical transformation studies. The Baeyer-Villiger oxidation experiments provided an interesting 3,5-seco-4-nor-triterpene skeleton via ring opening followed by an unusual rearrangement. A new methodology is described for transforming triterpenoids into 3,5-seco-4-nor derivatives.Article Citation - WoS: 18Citation - Scopus: 18A Computational Study on the Excited State Properties of a Cationic Cyanine Dye: Ttbc(Elsevier Ltd., 2011) Karaca, Sıla; Elmacı Irmak, Nuran; Elmacı, NuranThe ground and excited state behaviors of a biologically important mitochondria selective dye, 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzimidazolo carbocyanine (TTBC), were investigated in order to give useful information related to the enhancement of its electronic and optical properties. DFT and TDDFT levels of theory with different functionals and basis sets were used. The results obtained by using PBEPBE/6-31+G(d,p)/C-PCM are in good agreement with the experiments. The potential energy surface sections of TTBC were explored and the geometry optimized in the first excited state, S 1, to analyze the fluorescence spectrum of the dye. There are two distinct minima on the S 1 surface, one located near the ground state geometry and an energetically favorable twisted geometry, having a charge transfer character. The observation of similar ground and excited state dipoles as well as solvent-independent fluorescence and absorption wavelengths reveals that there is no competition between the two minima; the emission is dominantly coming from the more planar configuration.Article Citation - WoS: 107Citation - Scopus: 112Heterogeneous Suzuki Reactions Catalyzed by Pd(0)-Y Zeolite(Elsevier Ltd., 2004) Artok, Levent; Bulut, HaticeThe Pd(0)-Y zeolite showed high activity in the Suzuki cross-coupling reactions of aryl bromides without added ligands. The type of base and organic solvent were found to be critical for the efficiency of the reaction. The presence of water was essential within the reaction medium. The coupling reactions occurred on the external surface of the zeolite. The catalyst is reusable.Article Citation - WoS: 56Citation - Scopus: 59Suzuki Cross-Coupling Reaction of Aryl Halides With Arylboronic Acids Catalysed by Pd(ii)-Nay Zeolite(Elsevier Ltd., 2003) Bulut, Hatice; Artok, Levent; Yılmaz, SelahattinPd(II)-exchanged NaY zeolite showed high activity in the Suzuki cross-coupling reactions of aryl bromides and iodides without added ligands. The DMF:water ratio, and the type and amount of base were found to be critical for the efficiency of the reaction. The catalyst is reusable after regeneration.