Comparison of resonance Raman spectra of Ddh and Did molecular forms of octaethylporphinatonickel(Il) (NiOEP) indicates high-frequency bands at 1660, 1609, 1581, and 1524 cm-1 are structure-sensitive. Upon deuteration at the meso carbons two additional anomalously polarized bands appear with a concomitant decrease in intensity of the 1310-cm_1 anomalously polarized line. The spectrum in solution is consistent with a planar NiOEP structure. Spectra of CuOEP imply the existence of two molecular forms in this compound. An empirical correlation between the position of the anomalously polarized line at -! 590 cm-1 and the distance from the center of the porphyrin ring to the pyrrole nitrogen is applied to hemeprotein resonance Raman data. It is inferred that out-of-plane displacements of the iron atom are 0.4 Á in deoxyhemoglobin and 0.3 Á in fluoromethemoglobin.were formed18 by addition of excess dithionite to aqueous solutions of the ligated ferric porphyrin. A solution of pyridine protoporphyrin IX iron(II) was prepared at pH 6.8 by solubilizing the porphyrin with 3% sodium dodecylsulfate. FenOEP(L)2, L = imidazole or pyridine, were synthesized by a procedure of Kobayashi.19 CoinOEPX, X-= Bror CIO4-, were obtained by bromine oxidation or electrolysis.20 Samples of the two crystal forms of NiOEP were obtained with the conditions reported by Cullen and Meyer;12-13 however, the preparation of the tetragonal form was contaminated with triclinic crystals. The long needles, characteristic of the triclinic crystal, were removed manually. Triclinic crystals were prepared with hexane-dichloromethane solutions. Densities of the crystals agree with reported values.OctaethyIporphyrin-meso-d4. This compound was prepared21 from 2 -4 by exchange in D2SO4-D2O. After one exchange a minimum of 94% deuterium incorporation at the meso carbons was observed (*H NMR spectrum).Octaethylporphinato -meso-dd -nickel(II). The nickel was inserted in pyridine solvent. Following metal insertion, the solution was added to water and NiOEP extracted into CH2CI2. The solution was washed five times with water, dried over Na2S04, and filtered, and NiOEP crystallized from a CH2Cl2-hexane solution. The crystals were dried in vacuo at 150°. Deuterium incorporation at the meso carbons was 1 (dj), 4 (di), 9 (d3), and 86% (¿4).Chlorooctaethylporphinato-meso-d4-iron(III). Synthesis is the same as for the nickel compound, except DMF was employed as solvent. Deuterium incorporation was 92% (mass spectrum).Nitrosyletioporphyrinatocobalt. NO was bubbled slowly for 10 min into a CHCI3 solution of cobaltous etioporphyrin I. Stirring was continued for an additional 30 min under the NO atmosphere. Argon was bubbled through the solution to remove excess NO, methanol was added, and after 2 days dark purple crystals were formed. The crystals were filtered and washed with methanol: ir (KBr) 1665 cm-1 (NO).
This article describes a CuInS2 quantum dot (QD)-sensitized solar cell (QDSSC) with a multilayered architecture and a cascaded energy-gap structure fabricated using a successive ionic-layer adsorption and reaction process. We initially used different metal chalcogenides as interfacial buffer layers to improve unmatched band alignments between the TiO2 and CuInS2 QD sensitizers. In this design, the photovoltaic performance, in terms of the short-circuit current density (JSC), open-circuit voltage (VOC), fill factor (FF), and power conversion efficiency (PCE), was significantly improved. Both JSC and VOC were improved in CuInS2-based QDSSCs in the presence of interfacial buffer layers because of proper band alignment across the heterointerface and the negative band edge movement of TiO2. The PCE of CuInS2-based QDSSCs containing In2Se3 interfacial buffer layers was 1.35%, with JSC=5.83 mA/cm2, VOC=595 mV, and FF=39.0%. We also examined the use of alternative CdS and CdSe hybrid-sensitized layers, which were sequentially deposited onto the In2Se3/CuInS2 configuration for creating favorable cascaded energy-gap structures. Both JSC (11.3 mA cm(-2)) and FF (47.3%) for the CuInS2/CdSe hybrid-sensitized cells were higher than those for CuInS2-based cells (JSC=5.83 mA cm(-2) and FF=39.0%). In addition, the hybrid-sensitized cells had PCEs that were 1.3 times those of cells containing identically pretreated In2Se3 interfacial buffer layers. Additionally, we determined that ZnSe served as a good passivation layer on the surface of CuInS2/CdSe hybrid-sensitized QDs, prevented current leakage from the QDs to electrolytes, and lowered interfacial charge recombination. Under simulated illumination (AM 1.5, 100 mW cm(-2)), multilayered QDSSCs with distinct architectures delivered a maximum external quantum efficiency of 80% at 500 nm and a maximum PCE of 4.55%, approximately 9 times that of QDSSCs fabricated with pristine CuInS2.
Structural characterization of small molecule binding site hotspots within the global proteome is uniquely enabled by photoaffinity labeling (PAL) coupled with chemical enrichment and unbiased analysis by mass spectrometry (MS). MS-based binding site maps provide structural resolution of interaction sites in conjunction with identification of target proteins. However, binding site hotspot mapping has been confined to relatively simple small molecules to date; extension to more complex compounds would enable the structural definition of new binding modes in the proteome. Here, we extend PAL and MS methods to derive a binding site hotspot map for the immunosuppressant rapamycin, a complex macrocyclic natural product that forms a ternary complex with the proteins FKBP12 and FRB. Photorapamycin was developed as a diazirine-based PAL probe for rapamycin, and the FKBP12−photo-rapamycin−FRB ternary complex formed readily in vitro. Photoirradiation, digestion, and MS analysis of the ternary complex revealed a McLafferty rearrangement product of photo-rapamycin conjugated to specific surfaces on FKBP12 and FRB. Molecular modeling based on the binding site map revealed two distinct conformations of complex-bound photo-rapamycin, providing a 5.0 Å distance constraint between the conjugated residues and the diazirine carbon and a 9.0 Å labeling radius for the diazirine upon photoactivation. These measurements may be broadly useful in the interpretation of binding site measurements from PAL. Thus, in characterizing the ternary complex of photo-rapamycin by MS, we applied binding site hotspot mapping to a macrocyclic natural product and extracted precise structural measurements for interpretation of PAL products that may enable the discovery of new binding sites in the "undruggable" proteome.
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