Coincidence of checkerboard charge order and antinodal state decoherence in strongly underdoped superconducting Bi2Sr2CaCu2O8 + delta)

The doping dependence of nanoscale electronic structure in superconducting Bi(2)Sr(2)CaCu(2)O(8 + delta) is studied by scanning tunneling microscopy. At all dopings, the low energy density-of-states modulations are analyzed according to a simple model of quasiparticle interference and found to be consistent with Fermi-arc superconductivity. The superconducting coherence peaks, ubiquitous in near-optimal tunneling spectra, are destroyed with strong underdoping and a new spectral type appears. Exclusively in regions exhibiting this new spectrum, we find local "checkerboard" charge ordering of high energy states, with a wave vector of Q = (+/- 2pi/4.5a(0),0); (0, +/- 2pi/4.5a(0)) +/- 15%. Surprisingly, this spatial ordering of high energy states coexists harmoniously with the low energy Bogoliubov quasiparticle states.     

Formal syntheses of naturally occurring welwitindolinones

The formal syntheses of N-methylwelwitindolinone C isothiocyanate, N-methylwelwitindolinone C isonitrile, N-methylwelwitindolinone D isonitrile, 3-hydroxy-N-methylwelwitindolinone C isothiocyanate, and 3-hydroxy-N-methylwelwitindolinone C isonitrile are reported. The synthesis features several novel processes, including a Lewis acid mediated coupling between a benzylic-type heteroaromatic alcohol and a highly functionalized silyl ketene acetal, an intramolecular enolate arylation, and a regioselective, Pd(0)-catalyzed π-allylic cyclization of a γ-benzoyloxy enone moiety that is revealed by unmasking a furan ring.     

Studies toward welwitindolinones: formal syntheses of N-methylwelwitindolinone C isothiocyanate and related natural products

The formal syntheses of N-methylwelwitindolinone C isothiocyanate (4) and several other welwitindolinones 5–8 were achieved by the independent synthesis of 79. The synthesis featured a Lewis acid-mediated coupling between a heteroaryl carbinol and bis-TMS enol ether, an intramolecular enolate arylation, and an unprecedented intramolecular allylic alkylation of a γ-acyloxyenone.     

Forecasting continuous-time processes with applications to signal extraction

The paper derives forecasting and signal extraction estimates for continuous time processes. We present explicit formulas for filters and filter kernels that yield minimum mean square error estimates of future values of the process or an unobserved component, based on a continuum of values in the semi-infinite past. The class of processes considered are cumulations of moving average processes, which includes the CARIMA class. Explicit examples are calculated, and some discussion of applications to signal extraction is provided. We also provide an explicit algorithm for spectral factorization of continuous-time moving averages.     

Global intercompany assessment of ICIEF platform comparability for the characterization of therapeutic proteins

An international team spanning 19 sites across 18 biopharmaceutical and in vitro diagnostics companies in the United States, Europe, and China, along with one regulatory agency, was formed to compare the precision and robustness of imaged CIEF (ICIEF) for the charge heterogeneity analysis of the National Institute of Standards and Technology (NIST) mAb and a rhPD-L1-Fc fusion protein on the iCE3 and the Maurice instruments. This information has been requested to help companies better understand how these instruments compare and how to transition ICIEF methods from iCE3 to the Maurice instrument. The different laboratories performed ICIEF on the NIST mAb and rhPD-L1-Fc with both the iCE3 and Maurice using analytical methods specifically developed for each of the molecules. After processing the electropherograms, statistical evaluation of the data was performed to determine consistencies within and between laboratory and outlying information. The apparent isoelectric point (pI) data generated, based on two-point calibration, for the main isoform of the NIST mAb showed high precision between laboratories, with RSD values of less than 0.3% on both instruments. The SDs for the NIST mAb and the rhPD-L1-Fc charged variants percent peak area values for both instruments are less than 1.02% across different laboratories. These results validate the appropriate use of both the iCE3 and Maurice for ICIEF in the biopharmaceutical industry in support of process development and regulatory submissions of biotherapeutic molecules. Further, the data comparability between the iCE3 and Maurice illustrates that the Maurice platform is a next-generation replacement for the iCE3 that provides comparable data.     

Effects of pairing potential scattering on Fourier-transformed inelastic tunneling spectra of high-Tc cuprate superconductors with bosonic modes

Recent scanning tunneling microscopy (STM) experimentally observed strong gap inhomogeneity in Bi2Sr2CaCu2O(8+delta) (BSCCO). We argue that disorder in the pair potential underlies the gap inhomogeneity, and investigate its role in the Fourier-transformed inelastic tunneling spectra as revealed in the STM. We find that the random pair potential induces unique q-space patterns in the local density of states (LDOS) of a d-wave superconductor. We consider the effects of electron coupling to various bosonic modes and find the pattern of LDOS modulation due to coupling to the B(1g) phonon mode to be consistent with the one observed in the inelastic electron tunnneling STM experiment in BSCCO. These results suggest strong electron-lattice coupling as an essential part of the superconducting state in high-Tc materials.     

Stereocontrolled synthesis of δ-hydroxy allylic phosphine oxides by allylic ester transposition

The title compounds (3) were synthesised by stereospecific [1,3] rearrangement, controlled by the Ph₂PO group, from single isomers of the Horner-Wittig adducts (1)     

Synthesis of macrocyclic,potential protease inhibitors using a generic scaffold

A generic macrocyclic peptide structure 2 was designed as a potential inhibitor of a range of proteinases, by using as a basis for the design the known structures of a series of enzyme-inhibitor complexes. The macrocyclic nature of the target 2 was chosen so as to reduce the entropic advantage in the hydrolytic enzymatic step, and thereby to inhibit the function of the enzyme. The nature of the linking group was identified as a benzoxazole by molecular modeling, so as to preserve the recognized conformation of the peptide chain. The specificity of the potential inhibitor was tuned by variation of the P(1) group (by incorporating phenylalanine, aspartic acid, or lysine), to allow recognition by different enzyme classes. The targets were prepared from the bis-amino acid derivative 5, itself prepared using the Pd-catalyzed coupling of an organozinc reagent with the iodobenzothiazole 7 and subsequent macrocyclization of the open-chain derivatives 22-24 using HATU. None of the macrocylic compounds 25, 28-30, and 32 inhibited their target enzymes. NMR and MS studies on the interaction of macrocycle 29 and chymotrypsin established that compound 29 was in fact a substrate of the enzyme. This result indicated that while the design had been partially successful in identifying a compound that bound, the reduction in entropic advantage due to its macrocyclic nature was not sufficient to allow 29 to act as an inhibitor.     

Application of palladium-catalyzed allylic arylation to the synthesis of a (+/-)-7-deoxypancratistatin analogue

Palladium-catalyzed coupling of an aryl siloxane and an allylic carbonate proceeded in good yield to give an adduct that was converted to an analogue of (+/-)-7-deoxypancratistatin.