The self-assembly of peptide YYKLVFFC based on a fragment of the amyloid beta (A beta) peptide, A beta 16-20, KLVFF has been studied in aqueous solution. The peptide is designed with multiple functional residues to examine the interplay between aromatic interactions and charge on the self-assembly, as well as specific transformations such as the pH-induced phenol-phenolate transition of the tyrosine residue. Circular dichroism (CD) and Fourier-transform infrared (FTIR) spectroscopies are used to investigate the conditions for beta-sheet self-assembly and the role of aromatic interactions in the CD spectrum as a function of pH and concentration. The formation of well-defined fibrils at pH 4.7 is confirmed by cryo-TEM (transmission electron microscope) and negative stain TEM. The morphology changes at higher pH, and aggregates of short twisted fibrils are observed at pH 11. Polarized optical microscopy shows birefringence at a low concentration (1 wt.-%) of YYKLVFFC in aqueous solution, and small-angle X-ray scattering was used to probe nematic phase formation in more detail. A pH-induced transition from nematic to isotropic phases is observed on increasing pH that appears to be correlated to a reduction in aggregate anisotropy upon increasing pH.

Synchrotron radiation circular dichroism (SRCD) is a well-established method in structural biology. The first UV-VIS beamline dedicated to circular dichroism at Diamond Light Source, a third generation synchrotron facility in South Oxfordshire, has recently become operational and it is now available for the user community. Herein we present an important application of SRCD: the CD measurement of protein solutions in fused silica rectangular capillary cells. This was achieved without the use of any lens between the photoelastic modulator and the photomultiplier tube detectors by exploiting the high photon flux of the collimated beam that can be as little as half a millimeter squared. Measures to minimize or eliminate vacuum-UV protein denaturation effects are discussed. The CD spectra measured in capillaries is a proof of principle to address CD measurements in microdevice systems using the new B23 SRCD beamline.

In the paper by Hussainet al.[(2015),J. Synchrotron Rad.22, 465–468], Daniel Myatt is missing from the list of authors. The complete list of authors should be Rohanah Hussain, Kristian Benning, Daniel Myatt, Tamas Javorfi, Edoardo Longo, Timothy R. Rudd, Bill Pulford and Giuliano Siligardi.

Abstract. Previous clinical research has suggested high-affinity binding of flavopiridol (FLAP) to human blood serum proteins, specifically either human serum albumin (HSA) or human alpha-1-acid glycoprotein (hAGP), when compared to fetal bovine serum albumin (BSA) or bovine alpha-1-acid glycoprotein (bAGP) used in pre-clinical assays. This high-affinity binding was suggested as the reason for its poor human clinical trial performance as a treatment for chronic lymphocytic leukaemia (CLL). Using three biophysical techniques, specifically circular dichroism (CD), isothermal calorimetry (ITC) and fluorescence spectroscopy, I show that FLAP does not have an overly high-affinity for either fetal BSA, HSA, bAGP or hAGP. I therefore suggest an alternate hypothesis that models the albumin and alpha-1-acid glycoprotein (AGP) binding sites at the different protein concentrations used in the fetal bovine pre-clinical assay and human physiological conditions. I use analytical ultracentrifugation (AUC) experiments to determine the validity of the theoretical models. The models can also be altered to account for the elevated AGP levels and reduced albumin levels seen in human cancer patients. Major differences in the concentrations of free available FLAP are observed between the fetal bovine pre-clinical model and human physiological conditions. A number of recommendations can therefore be made on how future pre-clinical assay studies should be conducted.

The inherent flexibility of carbohydrates is dependent on stereochemical arrangements, and characterization of their influence and importance will give insight into the three-dimensional structure and dynamics. In this study, a β-(1→4)/β-(1→3)-linked glucosyl decasaccharide is experimentally investigated by synchrotron small-angle X-ray scattering from which its radius of gyration (R) is obtained. Molecular dynamics (MD) simulations of the decasaccharide show four populated states at each glycosidic linkage, namely, syn- and anti-conformations. The calculated R values from the MD simulation reveal that in addition to syn-conformers the presence of anti-ψ conformational states is required to reproduce experimental scattering data, unveiling inherent glycosidic linkage flexibility. The CHARMM36 force field for carbohydrates thus describes the conformational flexibility of the decasaccharide very well and captures the conceptual importance that anti-conformers are to be anticipated at glycosidic linkages of carbohydrates.