Jason Maley

Potential implications of endogenous aldehydes in β‐amyloid misfolding, oligomerization and fibrillogenesis

Aldehydes are capable of inducing protein cross‐linkage. An increase in aldehydes has been found in Alzheimers disease. Formaldehyde and methylglyoxal are produced via deamination of, respectively, methylamine and aminoacetone catalyzed by semicarbazide‐sensitive amine oxidase (SSAO, EC 1.4.3.6. The enzyme is located on the outer surface of the vasculature, where amyloidosis is often initiated. A high SSAO level has been identified as a risk factor for vascular disorders. Serum SSAO activity has been found to be increased in Alzheimers patients. Malondialdehyde and 4‐hydroxynonenal are derived from lipid peroxidation under oxidative stress, which is also associated with Alzheimers disease. Aldehydes may potentially play roles in β‐amyloid aggregation related to the pathology of Alzheimers disease. In the present study, thioflavin‐T fluorometry, dynamic light scattering, circular dichroism spectroscopy and atomic force microscopy were employed to reveal the effect of endogenous aldehydes on β‐amyloid at different stages, i.e. β‐sheet formation, oligomerization and fibrillogenesis. Formaldehyde, methylglyoxal and malondialdehyde and, to a lesser extent, 4‐hydroxynonenal are not only capable of enhancing the rate of formation of β‐amyloid β‐sheets, oligomers and protofibrils but also of increasing the size of the aggregates. The possible relevance to Alzheimers disease of the effects of these aldehydes on β‐amyloid deposition is discussed.

Barley Grain Constituents, Starch Composition, and Structure Affect Starch in Vitro Enzymatic Hydrolysis

The relationship between starch physical properties and enzymatic hydrolysis was determined using ten different hulless barley genotypes with variable carbohydrate composition. The ten barley genotypes included one normal starch (CDC McGwire), three increased amylose starches (SH99250, SH99073, and SB94893), and six waxy starches (CDC Alamo, CDC Fibar, CDC Candle, Waxy Betzes, CDC Rattan, and SB94912). Total starch concentration positively influenced thousand grain weight (TGW) (r(2) = 0.70, p < 0.05). Increase in grain protein concentration was not only related to total starch concentration (r(2) = -0.80, p < 0.01) but also affected enzymatic hydrolysis of pure starch (r(2) = -0.67, p < 0.01). However, an increase in amylopectin unit chain length between DP 12-18 (F-II) was detrimental to starch concentration (r(2) = 0.46, p < 0.01). Amylose concentration influenced granule size distribution with increased amylose genotypes showing highly reduced volume percentage of very small C-granules (<5 μm diameter) and significantly increased (r(2) = 0.83, p < 0.01) medium sized B granules (5-15 μm diameter). Amylose affected smaller (F-I) and larger (F-III) amylopectin chains in opposite ways. Increased amylose concentration positively influenced the F-III (DP 19-36) fraction of longer DP amylopectin chains (DP 19-36) which was associated with resistant starch (RS) in meal and pure starch samples. The rate of starch hydrolysis was high in pure starch samples as compared to meal samples. Enzymatic hydrolysis rate both in meal and pure starch samples followed the order waxy > normal > increased amylose. Rapidly digestible starch (RDS) increased with a decrease in amylose concentration. Atomic force microscopy (AFM) analysis revealed a higher polydispersity index of amylose in CDC McGwire and increased amylose genotypes which could contribute to their reduced enzymatic hydrolysis, compared to waxy starch genotypes. Increased β-glucan and dietary fiber concentration also reduced the enzymatic hydrolysis of meal samples. An average linkage cluster analysis dendrogram revealed that variation in amylose concentration significantly (p < 0.01) influenced resistant starch concentration in meal and pure starch samples. RS is also associated with B-type granules (5-15 μm) and the amylopectin F-III (19-36 DP) fraction. In conclusion, the results suggest that barley genotype SH99250 with less decrease in grain weight in comparison to that of other increased amylose genotypes (SH99073 and SH94893) could be a promising genotype to develop cultivars with increased amylose grain starch without compromising grain weight and yield.

Electronic structure of TiO2 nanotube arrays from X-ray absorption near edge structure studies

We report an X-ray absorption near edge structure (XANES) investigation of several TiO2nanotube arrays, including the as-prepared nanotube arrays from electrochemical anodic oxidation of Ti foil (as-prepared ATNTA), as-prepared nanotube arrays after annealing at 580 °C (annealed ATNTA) and annealed ATNTA after electrochemical intercalation with Li (Li-intercalated ATNTA). XANES at the O K-edge and Ti L3,2 and K edges shows distinctly different spectral features for the as-prepared and the annealed ATNTA, characteristic of amorphous and anatase structures, respectively. Intercalation of Li into annealed ATNTA induces a surprising, yet spectroscopically unmistakable, anatase to rutile transition. XANES at the Li K-edge clearly shows ionic features of Li in ATNTA. The charge relocation from Ti 3d to O 2p at the conduction band in TiO2 was also observed when Li ions were intercalated into annealed ATNTA albeit no noticeable reduction of Ti4+ to Ti 3+ was observed. The O K-edge shows a distinctly enhanced feature in the multiple scattering regime, indicating a close to linear O–Li–O arrangement in Li-intercalated ATNTA. These results show bonding changes between Ti and O resulting from the interaction of Li ions in the TiO2 lattices. Such bonding variation has also been supported by X-ray excited optical luminescence (XEOL), which suggests Li+-defect interactions. The implications of these results are discussed.

Nano-scale chemical imaging of a single sheet of reduced graphene oxide

Scanning transmission X-ray microscopy (STXM) has been used to chemically image single and multiple layers of a thermally reduced graphene oxide (r-GO) multi-layer sheet of the size of ∼1 μm and a thickness of ∼5 nm. The thickness of individual layers in the single sheet can be identified through quantitative analysis of STXM. The local electronic and chemical structure of interest (edge versus center) in different regions within the single r-GO sheet has been studied by C K-edge X-ray absorption near edge structure spectroscopy (XANES) with 30 nm spatial resolution. High and localized unoccupied densities of states (DOS) of carbon σ* character were observed in r-GO compared to graphite and were interpreted as the lack of strong layer to layer interaction in the former. The azimuthal dependence of C K-edge XANES in selected locations has also been obtained and was used to infer the preferred edge structure. The r-GO sample was also characterized by TEM, AFM and Raman spectroscopy; the findings are in good accord with the STXM results.

Lysine-functionalized nanodiamonds: synthesis, physiochemical characterization, and nucleic acid binding studies

Purpose: Detonation nanodiamonds (NDs) are carbon-based nanomaterials that, because of their size (4–5 nm), stable inert core, alterable surface chemistry, fluorescence, and biocompatibility, are emerging as bioimaging agents and promising tools for the delivery of biochemical molecules into cellular systems. However, diamond particles possess a strong propensity to aggregate in liquid formulation media, restricting their applicability in biomedical sciences. Here, the authors describe the covalent functionalization of NDs with lysine in an attempt to develop nanoparticles able to act as suitable nonviral vectors for transferring genetic materials across cellular membranes. Methods: NDs were oxidized and functionalized by binding lysine moieties attached to a three-carbon-length linker (1,3-diaminopropane) to their surfaces through amide bonds. Raman and Fourier transform infrared spectroscopy, zeta potential measurement, dynamic light scattering, atomic force microscopic imaging, and thermogravimetric analysis were used to characterize the lysine-functionalized NDs. Finally, the ability of the functionalized diamonds to bind plasmid DNA and small interfering RNA was investigated by gel electrophoresis assay and through size and zeta potential measurements. Results: NDs were successfully functionalized with the lysine linker, producing surface loading of 1.7 mmol g−1 of ND. These modified NDs formed highly stable aqueous dispersions with a zeta potential of 49 mV and particle size of approximately 20 nm. The functionalized NDs were found to be able to bind plasmid DNA and small interfering RNA by forming nanosized “diamoplexes”. Conclusion: The lysine-substituted ND particles generated in this study exhibit stable aqueous formulations and show potential for use as carriers for genetic materials.

Evaluating the cytotoxicity of flaxseed orbitides for potential cancer treatment

Flaxseed as well as its oil component possess antitumor activities against different types of cancer and have been used by some patients as complementary and/or alternative medicine. Linoorbitides (LOBs) are one family of flaxseed compounds that has implications for anticancer and antioxidant activity. The cytotoxicity of [1-9-NαC]-linusorb-B3 (LOB3), [1-9-NαC]-linusorb-B2 (LOB2), [1-9-NαC],[1-Rs,Ss-MetO]-linusorb-B2 ([MetO]-LOB2) and [1-8-NαC],[1-Rs,Ss-MetO]-linusorb-B1 ([MetO]-LOB1) was measured against human breast cancer Sk-Br-3 and MCF7 cell lines and melanoma A375 cell line. Overall cytotoxicity is cell-type specific. It scales as the hydrophobicity and concentration of the LOBs with the most abundant LOB3 being the most cytotoxic. Oral administration of LOB3 as a potential therapeutic agent might not be applicable as a much too high and/or frequent dose would be required to achieve a serum concentration of 400–500 μg/mL due to bioavailability and pharmacokinetic factors. However, LOB3 may be suitable for topical treatment formulations or as a lead compound in developing anticancer LOB derivatives.

Biomolecular interaction study of Cyclolinopeptide A with human serum albumin.

The kinetics, energetics, and structure of Cyclolinopeptide A binding with Human Serum Albumin were investigated with surface plasmon resonance and circular dichroism. The complex is formed through slow recognition kinetics that is temperature sensitive in the range of 20°C–37°C. The overall reaction was observed to be endothermic (ΔH = 204 kJ mol−1) and entropy driven (ΔS = 746 J mol−1K−1) with overall small changes to the tertiary structure.

In vitro characterization of ligand-induced oligomerization of the S. cerevisiae G-protein coupled receptor, Ste2p.

BACKGROUND The S. cerevisiae alpha-factor receptor, Ste2p, is a G-protein coupled receptor that plays key roles in yeast signaling and mating. Oligomerization of Ste2p has previously been shown to be important for intracellular trafficking, receptor processing and endocytosis. However the role of ligand in receptor oligomerization remains enigmatic. METHODS Using functional recombinant forms of purified Ste2p, atomic force microscopy, dynamic light scattering and chemical crosslinking are applied to investigate the role of ligand in Ste2p oligomerization. RESULTS Atomic force microscopy images indicate a molecular height for recombinant Ste2p in the presence of alpha-factor nearly double that of Ste2p alone. This observation is supported by complementary dynamic light scattering measurements which indicate a ligand-induced increase in the polydispersity of the Ste2p hydrodynamic radius. Finally, chemical cross-linking of HEK293 plasma membranes presenting recombinant Ste2p indicates alpha-factor induced stabilization of the dimeric form and higher order oligomeric forms of the receptor upon SDS-PAGE analysis. CONCLUSIONS alpha-factor induces oligomerization of Ste2p in vitro and in membrane. GENERAL SIGNIFICANCE These results provide additional evidence of a possible role for ligand in mediation of Ste2p oligomerization in vivo.

Spontaneous Ag-Nanoparticle Growth at Single-Walled Carbon Nanotube Defect Sites: A Tool for In Situ Generation of SERS Substrate

Silver nanoparticles were spontaneously formed on pristine and oxidized single-wall nanotubes. Nanoparticles were observed on carbon nanotubes with AFM, and the presence of Ag nanoparticles were confirmed by ESR experiments. Raman spectroscopy of the Ag-treated carbon nanotubes had a 4–10X enhancement of intensity compared to untreated carbon nanotubes. Ag nanoparticles formed at defect sites on the CNT surface, where free electrons located at the defect sites reduced Ag

Chemical and Structural Information from the Enamel of a Troodon Tooth Leading to an Understanding of Diet and Environment

Synchrotron micro X-ray fluorescence (XRF) spectroscopy with two-dimensional element mapping, micro X-ray diffraction (XRD), electron spin resonance spectroscopy (ESR) and atomic force microscopy (AFM) were used to investigate the chemical and structural nature of the enamel of a tooth from Troodon, a small theropod dinosaur. These methods show that the crystallites in the Troodon tooth are submicron-sized carbonated calcium hydroxyapatite, which are semi-randomly oriented with a preferred orientation of (002) towards the surface of the tooth. Transition metal ions are distributed in the voids between crystallite clusters. Comparison of the ESR spectra indicates that the Troodon tooth had less exposure to UV than a fossilized crocodile tooth.