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Silicon nanocrystals (Si NCs) are intensively studied for optoelectronic and biological applications due to having highly attractive features such as band engineering. Although doping is often used to control the optical and electrical properties, the related structural properties of solely doped and codoped Si NCs are not well-understood. In this study, we report the boron (B) and/or phosphorus (P) distribution in Si NCs embedded in borosilicate glass (BSG), phosphosilicate glass (PSG), and borophosphosilicate glass (BPSG) using atom probe tomography (APT). We compared solely and codoped Si NCs grown at different temperatures so that we may compare the effects of codoping and temperature on the B and/or P distribution. Proximity histograms and cluster analyses reveal that there exist boron-rich layers surrounding Si NCs and also B–P clusters within the Si NCs. Raman spectra also show a structural change between codoped Si NCs in solids and free-standing codoped Si NCs. These results lead us to understand that codoped Si NCs disperse in polar solvents.

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Abstract-Recent establishment of a sensitive ELISA system using antibodies against malondialdehyde-modified low density lipoprotein (MDA-LDL) made it possible to determine the circulating oxidized lipoprotein levels. Here, we investigated the serum levels of MDA-LDL in 62 patients with coronary artery disease (CAD) compared with the levels in 42 patients without CAD [groups CAD(ϩ) and CAD(Ϫ), respectively], which are adjusted for age, serum total cholesterol, LDL and high density lipoprotein cholesterol, and triglyceride levels. Serum MDA-LDL levels were 113.4Ϯ49.1 IU/L in CAD(ϩ), which were significantly higher than the levels in CAD(Ϫ) (85.2Ϯ22.5 IU/L, PϽ0.0005).The ratio of MDA-LDL/LDL cholesterol was 0.95Ϯ0.32 in CAD(ϩ), indicating a significant increase compared with the ratio in CAD(Ϫ) (0.68Ϯ0.19, PϽ0.0005). The positive correlation of MDA-LDL level and the ratio of MDA-LDL/LDL cholesterol with intima-media thickness in carotid arteries was observed. Age was not clearly associated with the MDA-LDL level (Pϭ0.865). The serum MDA level was positively correlated with LDL cholesterol (PϽ0.0001) and with triglycerides (PϽ0.001) and negatively correlated with high density lipoprotein cholesterol (PϽ0.05). Furthermore, the MDA-LDL level was negatively correlated with the peak size of the LDL particle (PϽ0.01).The LDL subclasses that were identified by using the sera collected from the subjects by sequential ultracentrifugation showed that the ratios of MDA-LDL/apolipoprotein B in LDL3 and LDL4 were nearly 3-fold higher than those in LDL1 and LDL2 for CAD(ϩ) and CAD(Ϫ). These results indicate that the circulating MDA-LDL level is increased in CAD(ϩ), independent of the serum LDL cholesterol level but in association with the peak size of LDL particles.

Understanding the role of the L/D-stereospecificity of amino acids is important in obtaining further insight into the mechanism of the formation of amyloid fibrils. Beta(2)-microglobulin is a major component of amyloid fibrils deposited in patients with dialysis-related amyloidosis. A 22-residue peptide of beta(2)-microglobulin, Ser20-Lys41 (L-K3 peptide), obtained by digestion with Acromobacter protease I, formed amyloid-like fibrils in 50% (v/v) 2,2,2-trifluoroethanol and 10 mM HCl at 25 degrees C, as confirmed by thioflavin T fluorescence, circular dichroism spectra, and atomic force microscopy images. A synthetic K3 peptide composed of D-amino acids (D-K3 peptide) formed similar fibrils but with opposite chirality as indicated by circular dichroism spectra. A mixture of L-K3 and D-K3 peptides also formed fibrils, although the L- and D-amino acid composition of each fibril is unknown. To examine the possible cross-reactivity between L- and D-enantiomers, we carried out seeding experiments in which preformed seeds were extended by monomers. The results revealed that only the homologous extensions proceed smoothly, i.e., the growth of L-seeds by L-monomers or D-seeds by D-monomers. The results suggest that, while the fibrils derived from L- and D-peptides form in a similar manner but with opposite stereochemistry, a cross-reaction between them is prevented because the geometry of the mixed sheet cannot satisfy dominant factors for beta-sheet stabilization.

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Abstract␤ 2 -Microglobulin (␤2-m) is a major component of dialysis-related amyloid fibrils. Although recombinant ␤2-m forms needle-like fibrils by in vitro extension reaction at pH 2.5, reduced ␤2-m, in which the intrachain disulfide bond is reduced, cannot form typical fibrils. Instead, thinner and flexible filaments are formed, as shown by atomic force microscopy images. To clarify the role of the disulfide bond in amyloid fibril formation, we characterized the conformations of the oxidized (intact) and reduced forms of ␤2-m in the acid-denatured state at pH 2.5, as well as the native state at pH 6.5, by heteronuclear NMR. { 1 H}-15 N NOE at the regions between the two cysteine residues (Cys25-Cys80) revealed a marked difference in the pico-and nanosecond time scale dynamics between that the acid-denatured oxidized and reduced states, with the former showing reduced mobility. Intriguingly, the secondary chemical shifts, ⌬C␣, ⌬CO, and ⌬H␣, and 3 J HNH␣ coupling constants indicated that both the oxidized and reduced ␤2-m at pH 2.5 have marginal ␣-helical propensity at regions close to the C-terminal cysteine, although it is a ␤-sheet protein in the native state. The results suggest that the reduced mobility of the denatured state is an important factor for the amylodogenic potential of ␤2-m, and that the marginal helical propensity at the C-terminal regions might play a role in modifying this potential.Keywords: Amyloid fibrils; atomic force microscopy; ␤ 2 -microglobulin; denatured state; disulfide bond; heteronuclear NMR; hydrogen/deuterium exchange Supplemental material: See www.proteinscience.org.An increasing number of proteins have been found to aggregate into insoluble fibers that cause various pathologic disorders in vivo. These fibers, collectively referred to as "amyloid fibrils," have common structural features (Gillmore et al. 1997;Kelly 1998). Recent studies have shown that several proteins that are not related to any disease can also form similar amyloid-like fibers (Brange et al. 1997;Guijarro et al. 1998;Ohnishi et al. 2000;Fezoui et al. 2001;Bucciantini et al. 2002), suggesting that such a conformation is common to many proteins. Under appropriate conditions, many proteins have the potential to assume this conformation. On the other hand, amyloid fibrils are homogeneous, and it is not possible to form chimeric fibrils composed of distinct amyloid proteins or peptides (Chien and Weissman 2001). This high species barrier suggests that amyloid fibrils are stabilized by specific interactions that Reprint requests to: Yuji Goto, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan; e-mail: ygoto@protein.osaka-u.ac.jp; fax: 81-6-6879-8616.Abbreviations: AFM, atomic force microscopy; ␤2-m, ␤ 2 -microglobulin; EM, electron microscopy; HSQC, heteronuclear single quantum coherence spectroscopy; NMR, nuclear magnetic resonance; NOE, nuclear Overhauser effect; NOESY, nuclear Overhauser enhancement spectroscopy; pD r , pH meter electrode reading without correction for...

This paper is the second in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and the certification of reference preparations. Other parts deal with: Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes; Part 3. Reference Procedure for the Measurement of Catalytic Concentration of Lactate Dehydrogenase; Part 4. Reference Procedure for the Measurement of Catalytic Concentration of Alanine Aminotransferase; Part 5. Reference Procedure for the Measurement of Catalytic Concentration of Aspartate Aminotransferase; Part 6. Reference Procedure for the Measurement of Catalytic Concentration of gamma-Glutamyltransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C. A document describing the determination of preliminary reference values is also in preparation. The pro- described 30 degrees C IFCC reference method (1). Differences are tabulated and commented on in Appendix 3.