Conformational and photophysical studies on porphyrin-containing donor-bridge-acceptor compounds. Charge separation in micellar nanoreactors

Photophysical studies with semi-rigid, 1, and flexible, 2, donor-bridge-acceptor (D-b-A2+) molecules with D a porphyrin and A2+ a methyl viologen moiety, were performed in neat polar solvents as well as included in surfactant (DTAB) aqueous and in reverse AOT/n-alkane micelles. The micelles acted as nanoreactors for the photoinduced electron transfer reaction upon laser excitation. In spite of the longer lifetime of the charge separated (CS) state in the semi-rigid tetrad 1(ca. 200 ns vs. ca. 100 ns for the flexible dyad 2), the CS formation quantum yield, for example in acetonitrile, was lower for the former (phi(CS) = 0.13) than for the latter (0.58). Comparison of the time-resolved fluorescence data in neat solvent and in the micelles yielded the phi(CS) values in the dilute micellar solutions. Application of laser-induced optoacoustic spectroscopy at various temperatures to 1 dissolved in a polar organic solvent (benzonitrile, BZN) included in aqueous DTAB nanoreactors afforded structural volume changes for the production in hundreds of ps of the CS state upon excitation of a polar molecule. The contraction during CS formation upon excitation of the collapsed conformer in BZN is attributed to the entering of solvent into the open molecular cavity. The opening upon formation of the CS state due to photoinduced electron transfer in the 1 collapsed conformation arises from the repulsion of the two positively charged ends in this state, as previously calculated. Inclusion of 1 in reverse AOT micelles in various n-alkanes also led to a contraction upon excitation, but the data had much more error due to the limited range of variability of the ratio of thermoelastic parameters. The data obtained with the more flexible "supermolecule" 2 showed the predicted large conformation flexibility of these molecules.     

The Preparation of Substituted Hydroxyphenyl-pyridyl-ethanols and α-Hydroxyphenyl-α-methylpyridineethanols by the Condensation of 2-, 3-, or 4-Picolyllithium with Select Hydroxy-benzaldehydes and 4-Hydroxyacetophenone

2-, 3-, or 4-Picolyllithium was prepared in excess lithium diiso-propylamide and condensed with several hydroxy-benzaldehydes and 4-hydroxy-acetophenone to afford substituted hydroxyphenyl-pyridyl-ethanols and α-hydroxyphenyl-α-methylpyridineethanols. In two instances. 3-picolyllithium condensed with aldehydes to presumably form the hydroxyphenyl-pyridyl-ethanol, which underwent linear dehydration to the substituted pyridyl-ethylenyl-phenol.     

Automated,high performance,flow-through chemiluminescence microarray for the multiplexed detection of phycotoxins

A novel multiplexed immunoassay for the analysis of phycotoxins in shellfish samples has been developed. Therefore, a regenerable chemiluminescence (CL) microarray was established which is able to analyze automatically three different phycotoxins (domoic acid (DA), okadaic acid (OA) and saxitoxin (STX)) in parallel on the analysis platform MCR3. As a test format an indirect competitive immunoassay format was applied. These phycotoxins were directly immobilized on an epoxy-activated PEG chip surface. The parallel analysis was enabled by the simultaneous addition of all analytes and specific antibodies on one microarray chip. After the competitive reaction, the CL signal was recorded by a CCD camera. Due to the ability to regenerate the toxin microarray, internal calibrations of phycotoxins in parallel were performed using the same microarray chip, which was suitable for 25 consecutive measurements. For the three target phycotoxins multi-analyte calibration curves were generated. In extracted shellfish matrix, the determined LODs for DA, OA and STX with values of 0.5 ± 0.3 μg L⁻¹, 1.0 ± 0.6 μg L⁻¹, and 0.4 ± 0.2 μg L⁻¹ were slightly lower than in PBS buffer. For determination of toxin recoveries, the observed signal loss in the regeneration was corrected. After applying mathematical corrections spiked shellfish samples were quantified with recoveries for DA, OA, and STX of 86.2%, 102.5%, and 61.6%, respectively, in 20 min. This is the first demonstration of an antibody based phycotoxin microarray.     

A new high: Cannabis as a budding source of carbon-based materials for electrochemical power sources

Cannabis sativa L., a low-cost, fast-growing herbaceous plant, is seeing a resurgence in widespread cultivation as a result of new policies and product drive. Its biodegradable and environmentally benign nature coupled with its high specific surface area and three-dimensional hierarchal structure makes it an excellent candidate for use as a biomass-derived carbon material for electrochemical power sources. It is proposed that this ‘wonder crop’ could have an important role in the energy transition by providing high-functioning carbon-based materials for electrochemistry. In this article, all instances of C. sativa usage in batteries, fuel cells and supercapacitors are discussed with a focus on highlighting the high capacity, rate capability, capacitance, current density and half-wave potential that can be achieved with its utilisation in the field.     

Efficient Krylov subspace methods for uncertainty quantification in large Bayesian linear inverse problems

Uncertainty quantification for linear inverse problems remains a challenging task, especially for problems with a very large number of unknown parameters (e.g., dynamic inverse problems) and for problems where computation of the square root and inverse of the prior covariance matrix are not feasible. This work exploits Krylov subspace methods to develop and analyze new techniques for large‐scale uncertainty quantification in inverse problems. In this work, we assume that generalized Golub‐Kahan‐based methods have been used to compute an estimate of the solution, and we describe efficient methods to explore the posterior distribution. In particular, we use the generalized Golub‐Kahan bidiagonalization to derive an approximation of the posterior covariance matrix, and we provide theoretical results that quantify the accuracy of the approximate posterior covariance matrix and of the resulting posterior distribution. Then, we describe efficient methods that use the approximation to compute measures of uncertainty, including the Kullback‐Liebler divergence. We present two methods that use the preconditioned Lanczos algorithm to efficiently generate samples from the posterior distribution. Numerical examples from dynamic photoacoustic tomography demonstrate the effectiveness of the described approaches.     

A photoactive isoprenoid diphosphate analogue containing a stable phosphonate linkage: synthesis and biochemical studies with prenyltransferases

A number of biochemical processes rely on isoprenoids, including the post-translational modification of signaling proteins and the biosynthesis of a wide array of compounds. Photoactivatable analogues have been developed to study isoprenoid utilizing enzymes such as the isoprenoid synthases and prenyltransferases. While these initial analogues proved to be excellent structural analogues with good cross-linking capability, they lack the stability needed when the goals include isolation of cross-linked species, tryptic digestion, and subsequent peptide sequencing. Here, the synthesis of a benzophenone-based farnesyl diphosphate analogue containing a stable phosphonophosphate group is described. Inhibition kinetics, photolabeling experiments, as well as X-ray crystallographic analysis with a protein prenyltransferase are described, verifying this compound as a good isoprenoid mimetic. In addition, the utility of this new analogue was explored by using it to photoaffinity label crude protein extracts obtained from Hevea brasiliensis latex. Those experiments suggest that a small protein, rubber elongation factor, interacts directly with farnesyl diphosphate during rubber biosynthesis. These results indicate that this benzophenone-based isoprenoid analogue will be useful for identifying enzymes that utilize farnesyl diphosphate as a substrate.     

Carbaporphyrinoid chemistry has a silver lining! silver(III) oxybenzi-, oxynaphthi-, tropi-, and benzocarbaporphyrins

[structure: see text] Carbaporphyrinoid systems with semiquinone, cycloheptatriene, or indene subunits react under mild conditions with silver(I) acetate to give stable silver(III) organometallic derivatives.     

Selective Pyrophosphate Recognition by Cyclic Peptide Receptors in Physiological Saline

The anion binding ability of a family of bis(Zn^II‐Dpa) functionalized cyclic peptides has been investigated using displacement assays with a fluorescent coumarin indicator in water, saline solution, and Krebs buffer. Non‐binding side‐chain steric bulk, the relative position of binding sites, and the scaffold size were all found to affect the ability of these receptors to discriminate between polyphosphate ions. Most receptors showed some selectivity for pyrophosphate over ATP and ADP in water and saline, and this selectivity was significantly enhanced in the biologically relevant Krebs buffer giving chemosensing ensembles capable of selective recognition of pyrophosphate in the presence of excess ATP.     

Development,validation, and implementation of capillary gel electrophoresis as a replacement for SDS‐PAGE for purity analysis of IgG2 mAbs

Capillary gel electrophoresis (CGE) methods with UV detection were developed for reduced and non‐reduced mAb analysis. These methods can be used to evaluate mAb purity, offering more reproducible quantitation compared with that of traditional SDS‐PAGE methods. These CGE methods have been utilized as platform technology for bioprocess development, formulation development, mAb characterization, drug substance/drug product release testing as well as a required methodology for stability testing. We have found these CGE methods to be applicable across a platform of mAbs in preclinical and clinical development, with the majority of mAbs requiring no modification to the method conditions. This methodology has been ICH validated and transferred to several supporting organizations. The data presented herein describes the development of CGE methodology, platform application to mAb purity analysis, ICH validation, reliability metrics, and considerations on technology enhancement for improved performance and throughput.