XPS and UPS study on band alignment at Pt-Zn-terminated ZnO(0 0 0 1) interface

The interface between Pt and Zn-terminated ZnO(0 0 0 1) was investigated by X-ray and ultra violet photoelectron spectroscopy in order to examine electronic band alignment. An angle-resolved X-ray photoelectron spectroscopy measurement of the clean ZnO(0 0 0 1) surface has revealed a downward band bending by 0.25 eV. The results of the valence band analysis show that the work function and the valence band maximum of clean ZnO(0 0 0 1) were 4.49 eV and 2.79 eV, respectively. Platinum was then deposited in several deposition steps onto a clean ZnO(0 0 0 1) surface up to 0.6 nm in thickness. After the deposition, the binding energy of Zn 2p doublet peak was shifted towards lower value by 0.77 eV, and the measured work function changed to 5.51 eV. As a result, the Schottky barrier height of Pt/ZnO(0 0 0 1) interface was 1.11 eV.     

Characterizations of graphs G having all [1,k]-factors in kG

Let $k\ge 1$ be an integer and $G$ be a graph. Let $kG$ denote the graph obtained from $G$ by replacing each edge of $G$ with $k$ parallel edges. We say that $G$ has all $[1,k]$-factors or all fractional $[1,k]$-factors if $G$ has an $h$-factor or a fractional $h$-factor for every function $h:V\left(G\right)\to \{1,2,\dots ,k\}$ with $h\left(V\left(G\right)\right)$ even. In this note, we come up with simple characterizations of a graph $G$ such that $kG$ has all $[1,k]$-factors or all fractional $[1,k]$-factors. These characterizations are extensions of Tutte’s 1-Factor Theorem and Tutte’s Fractional 1-Factor Theorem.     

Separation and quantification of monoclonal-antibody aggregates by hollow-fiber-flow field-flow fractionation

Hollow-fiber-flow field-flow fractionation (HF5) separates protein molecules on the basis of the difference in the diffusion coefficient, and can evaluate the aggregation ratio of proteins. However, HF5 is still a minor technique because information on the separation conditions is limited. We examined in detail the effect of different settings, including the main-flow rate, the cross-flow rate, the focus point, the injection amount, and the ionic strength of the mobile phase, on fractographic characteristics. On the basis of the results, we proposed optimized conditions of the HF5 method for quantification of monoclonal antibody in sample solutions. The HF5 method was qualified regarding the precision, accuracy, linearity of the main peak, and quantitation limit. In addition, the HF5 method was applied to non-heated Mab A and heat-induced-antibody-aggregate-containing samples to evaluate the aggregation ratio and the distribution extent. The separation performance was comparable with or better than that of conventional methods including analytical ultracentrifugation–sedimentation velocity and asymmetric-flow field-flow fractionation.     

Preparation of high molecular weight polybenzoxazine prepolymers containing siloxane unites and properties of their thermosets

High‐molecular‐weight polybenzoxazine prepolymers containing polydimethylsiloane unit in the main‐chain have been synthesized from α,ω‐bis(aminopropyl)polydimethylsiloxane (PDMS) (molecular weight = 248, 850, and 1622) and bisphenol‐A with formaldehyde. Moreover, another type of prepolymers was prepared using methylenedianiline (MDA) as codiamine with PDMS. The weight average molecular weight of the obtained prepolymers was estimated from size exclusion chromatography to be in the range of 8000–11,000. The chemical structures of the prepolymers were investigated by ¹H NMR and IR analyses. The prepolymers gave transparent free standing films by casting their dioxane solution. The prepolymer films after thermally cured up to 240 °C gave brown colored transparent and flexible polybenzoxazine films. Tensile test of the films revealed that the elongation at break increased with increasing the molecular weight of PDMS unit. Dynamic mechanical analysis of the thermosets showed that the T_gs were as high as 238–270 °C. The thermosets also revealed high thermal stability as evidenced by the 5% weight loss temperatures in the range of 324–384 °C from thermogravimetic analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of Four- and Five-Membered Heterocycles Derived from an Iminophosphorane

Reactions of an iminophosphorane bearing the Martin ligand with a ketone, an isothiocyanate, and an alkyne gave the corresponding cycloadducts, 1,3,2 u 5 -oxazaphosphetidine, 1,3,2 u 5 -diazaphosphetidine-4-thione, and 1,2 u 5 -azaphosphetine, respectively, while that with dimethyl acetylenedicarboxylate (DMAD) and successive hydrolysis afforded the 1,2 u 5 -oxaphosphole-(2 H )-one. Thermal reactions of the cycloadducts were also studied.     

Bioconjugation of Serum Albumin to a Maleimide‐appended Porphyrin/Cyclodextrin Supramolecular Complex as an Artificial Oxygen Carrier in the Bloodstream

HemoCD is an inclusion complex of per‐O‐methylated β‐cyclodextrin dimer and an iron(II) porphyrin, which forms a stable O₂ complex in water. Therefore, hemoCD has the potential for use as a synthetic O₂ carrier in mammalian blood. In this study, a hemoCD derivative having a maleimide group (Mal‐hemoCD) was conjugated to a Cys residue of serum albumin via a Michael addition reaction in order to increase the circulation time of the O₂ carrier. The O₂‐binding affinities (P_1/2 [Torr]) and half‐lives (t_1/2 [h]) of the O₂ adducts at pH 7.4 and 25 °C were determined to be 9 Torr and 23 h for Mal‐hemoCD, and 10 Torr and 14 h for albumin‐conjugated hemoCD (Alb‐hemoCD). Our pharmacokinetic study revealed that renal excretion of Alb‐hemoCD was effectively suppressed and that half of injected Alb‐hemoCD remained in blood at 3 h after injection. It is noteworthy that Mal‐hemoCD also had a long circulation time because of the bioconjugation reaction that occurred during circulation in the bloodstream.     

High-energy electron transfer dissociation (HE-ETD) using alkali metal targets for sequence analysis of post-translational peptides

Post-translational modifications (PTMs) of proteins are important in the activation, localization, and regulation of protein function in vivo. The usefulness of electron capture dissociation (ECD) and electron-transfer dissociation (ETD) in tandem mass spectrometry (MS/MS) using low-energy (LE) trap type mass spectrometer is associated with no loss of a labile PTM group regarding peptide and protein sequencing. The experimental results of high-energy (HE) collision induced dissociation (CID) using the Xe and Cs targets and LE-ETD were compared for doubly-phosphorylated peptides TGFLT(p)EY(p)VATR (1). Although HE-CID using the Xe target did not provide information on the amino acid sequence, HE-CID using the Cs target provided all the z-type ions without loss of the phosphate groups as a result of HE-ETD process, while LE-ETD using fluoranthene anion gave only z-type ions from z₅ to z₁₁. The difference in the results of HE-CID between the Xe and Cs targets demonstrated that HE-ETD process with the Cs target took place much more dominantly than collisional activation. The difference between HE-ETD using Cs targets and LE-ETD using the anion demonstrated that mass discrimination was much weaker in the high-energy process. HE-ETD was also applied to three other phosphopeptides YGGMHRQEX(p)VDC (2: X = S, 3: X = T, 4: X = Y). The HE-CID spectra of the doubly-protonated phosphopeptides (= [M + 2H]²⁺) of 2, 3, and 4 using the Cs target showed a very similar feature that the c-type ions from c₇ to c₁₁ and the z-type ions from z₇ to z₁₁ were formed via N-Cα bond cleavage without a loss of the phosphate group.     

A Designer Axially Chiral Amino Sulfonamide as an Efficient Organocatalyst for Direct Asymmetric Mannich Reactions of N‐Boc‐Protected Imines

The moderate nucleophilicity of the axially chiral amino sulfonamide (S)‐ 1 suppresses the problematic side reactions, including aldol reactions, in the asymmetric Mannich reaction of N‐Boc‐protected imines with aldehydes. The corresponding adducts are obtained in good yield and excellent stereoselectivity (see scheme; Boc=tert‐butoxycarbonyl, Tf=trifluoromethanesulfonyl).

     

Organocatalytic oxy-Michael addition of alcohols to α,β-unsaturated aldehydes

1,4-Addition of alcohols to α,β-unsaturated aldehydes was found to be efficiently promoted by biphenyldiamine-based catalyst 3 without formation of the acetals.