1.
Salts drive controllable multilayered upright assembly of amyloid-like peptides at mica/water interface.
Dai, B, Kang, SG, Huynh, T, Lei, H, Castelli, M, Hu, J, Zhang, Y, Zhou, R
Proceedings of the National Academy of Sciences of the United States of America. 2013;(21):8543-8
Abstract
Surface-assisted self-assembly of amyloid-like peptides has received considerable interest in both amyloidosis research and nanotechnology in recent years. Despite extensive studies, some controlling factors, such as salts, are still not well understood, even though it is known that some salts can promote peptide self-assemblies through the so-called "salting-out" effect. However, they are usually noncontrollable, disordered, amorphous aggregates. Here, we show via a combined experimental and theoretical approach that a conserved consensus peptide NH2-VGGAVVAGV-CONH2 (GAV-9) (from representative amyloidogenic proteins) can self-assemble into highly ordered, multilayered nanofilaments, with surprising all-upright conformations, under high-salt concentrations. Our atomic force microscopy images also demonstrate that the vertical stacking of multiple layers is highly controllable by tuning the ionic strength, such as from 0 mM (monolayer) to 100 mM (mainly double layer), and to 250 mM MgCl2 (double, triple, quadruple, and quintuple layers). Our atomistic molecular dynamics simulations then reveal that these individual layers have very different internal nanostructures, with parallel β-sheets in the first monolayer but antiparallel β-sheets in the subsequent upper layers due to their different microenvironment. Further studies show that the growth of multilayered, all-upright nanostructures is a common phenomenon for GAV-9 at the mica/water interface, under a variety of salt types and a wide range of salt concentrations.
2.
Synergistic effect of histone deacetylase inhibitors FK228 and m-carboxycinnamic acid bis-hydroxamide with proteasome inhibitors PSI and PS-341 against gastrointestinal adenocarcinoma cells.
Adachi, M, Zhang, Y, Zhao, X, Minami, T, Kawamura, R, Hinoda, Y, Imai, K
Clinical cancer research : an official journal of the American Association for Cancer Research. 2004;(11):3853-62
Abstract
PURPOSE We investigated whether the histone deacetylase inhibitors m-carboxycinnamic acid bis-hydroxamide (CBHA) and a bicyclic depsipeptide, FK228, can enhance the anticancer effect of the proteasome inhibitors PSI and PS-341 in gastrointestinal carcinoma cells. EXPERIMENTAL DESIGN The anticancer effect of CBHA or FK228 and PSI or PS-341 was evaluated by cell death, caspase-3 activity, externalization of phosphatidylserine and DNA fragmentation, and colony formation assay. Expression of apoptosis-related molecules and cell cycle regulatory molecules, as well as phosphorylation of p38 were investigated by immunoblots. Generation of reactive oxygen species (ROS) was detected by intracellular oxidation of 5- (and-6)-carboxy-2',7'-dichlorodihydrofluorescein diacetate. RESULTS CBHA or FK228 plus PSI or PS-341 synergistically induced apoptosis in human colonic DLD-1 and gastric MKN45 carcinoma cell lines. CBHA or FK228, but not 5-fluorouracil, plus PS-341 strongly decreased plating efficiency of DLD-1 cells. FK228 elicited ROS generation, and the free radical scavenger l-N-acetylcysteine inhibited the synergistic anticancer effect of combined therapy. In addition, l-N-acetylcysteine inhibited the combined therapy-mediated elevation of a proapoptotic BH3-only protein Bim expression, phosphorylation of H2AX, and accumulation of 8-hydroxydeoxyguanosine. CONCLUSIONS FK228 or CBHA and PSI or PS-341 synergistically induce apoptosis in DLD-1 and MKN45 cells depending on ROS-mediated signals. Our data suggest that a combination of FK228 or CBHA with PSI or PS-341 may be a valuable therapy against gastrointestinal adenocarcinoma cells.
3.
Isothermal titration calorimetry measurements of Ni(II) and Cu(II) binding to His, GlyGlyHis, HisGlyHis, and bovine serum albumin: a critical evaluation.
Zhang, Y, Akilesh, S, Wilcox, DE
Inorganic chemistry. 2000;(14):3057-64
Abstract
The binding of Ni(II) and Cu(II) to histidine, to the tripeptides GlyGlyHis and HisGlyHis, and to the protein bovine serum albumin has been studied by isothermal titration calorimetry (ITC) to determine the experimental conditions and data analysis necessary to reproduce literature values for the binding constants and thermodynamic parameters. From analysis of the ITC data, we find that there are two major considerations for the use of this method to accurately quantify metal ion interaction with biological macromolecules. First, to determine true pH-independent binding constants, ITC data must be corrected for metal ion competition with protons by accounting for the experimental pH and pKa values of the metal-binding residues. Second, metal interaction with the buffer (stability and enthalpy of formation of metal-buffer complex(es)) must be included in the analysis of the ITC data to determine the binding constants and the change in enthalpy. While it may be possible to use a buffer that forms only weak, and therefore negligible, complexes with the metal, a buffer that has a strong and well-characterized interaction has the benefit of suppressing metal ion hydrolysis and precipitation, and of allowing the quantification of high-affinity metal-binding sites on biological macromolecules. This study has also quantified the contribution of the N-terminal imidazole of HisGlyHis to the stability of the Cu(II) and Ni(II) complexes of this protein sequence and has provided new insight about Cu(II) binding to albumin.