Cleaving Direct‐Laser‐Written Microstructures on Demand

Using an advanced functional photoresist we introduce direct‐laser‐written (DLW) 3D microstructures capable of complete degradation on demand. The networks consist exclusively of reversible bonds, formed by irradiation of a phenacyl sulfide linker, giving disulfide bonds in a radical‐free step‐growth polymerization via a reactive thioaldehyde. The bond formation was verified in solution by ESI‐MS. To induce cleavage, dithiothreitol causes a thiol–disulfide exchange, erasing the written structure. The mild cleavage of the disulfide network is highly orthogonal to other, for example, acrylate‐based DLW structures. To emphasize this aspect, DLW structures were prepared incorporating reversible structural elements into a non‐reversible acrylate‐based standard scaffold, confirming subsequent selective cleavage. The high lateral resolution achievable was verified by the preparation of well‐defined line gratings with line separations of down to 300 nm.     

Aminophosphinic Acids in a Pyridine Series: Cleavage of Pyridine-2- and Pyridine-4-methyl(amino)phosphinic Acids in Acidic Solutions

The synthesis of a series of new pyridine aminomethylphosphinic acids is described. These compounds were obtained in the reaction of the corresponding pyridine aldehydes with primary amines and with ethyl phenylphosphinate, or methylphosphinate, in the presence of bromotrimethylsilane. In aqueous, strong acid solutions, pyridine aminophosphinic acids were split, forming the phenyl-, or methylphosphonic, acid and the corresponding secondary pyridyl-alkylamines. The kinetics of some observed cleavages were measured, and a mechanism of the cleavage has been proposed.     

The ornithine effect in peptide cation dissociation

Facile cleavage C‐terminal to ornithine residues in gas phase peptides has been observed and termed the ornithine effect. Peptides containing internal or C‐terminal ornithine residues, which are formed from deguanidination of arginine in solution, were fragmented to produce either a y‐ion or water loss, respectively, and the complementary b‐ion. The fragmentation patterns of several peptides containing arginine were compared to those of the ornithine analogues. Conversion of arginine to ornithine results in a decrease of the gas phase proton affinity of the residue, thereby increasing the mobility of the ionizing proton. This alteration allows the nucleophilic amine to facilitate a neighboring group reaction to induce a cleavage of the adjacent amide bond. The selective cleavage at the ornithine residue is proposed to result from the highly favorable generation of a six‐membered lactam ring. The ornithine effect was compared with the well‐known proline and aspartic acid effects in peptide fragmentation using angiotensin II, DRVYIHPF and the ornithine analogue, DOVYIHPF. Under conditions favorable to either the aspartic acid (i.e. singly protonated peptide) or proline effect (i.e. doubly protonated peptide), the ornithine effect was consistently observed to be the more favorable fragmentation pathway. The highly selective nature of the ornithine effect opens up the possibility for conversion of arginine to ornithine residues to induce selective cleavages in polypeptide ions. Such an approach may complement strategies that seek to generate non‐selective cleavages of the related peptides. Copyright © 2013 John Wiley & Sons, Ltd.     

Identification of reducing and nonreducing neutral carbohydrates by laser‐enhanced in‐source decay (LEISD) MALDI MS

In this work, laser‐enhanced in‐source decay (LEISD) technique of matrix‐assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI‐FT‐ICR‐MS) was used to distinguish reducing and nonreducing carbohydrates. Interestingly, easier cleavage of (1 → 2)‐linked glycosidic bonds for nonreducing carbohydrates containing D‐fructofuranosyl units was observed in MALDI‐FT‐ICR‐MS, which was in agreement with the result of theoretical calculation by the software package Gaussian 09. Importantly, no cross‐ring cleavage of fructofuranosyl residues was detected in the LEISD spectra of nonreducing carbohydrates. LEISD method therefore offers an attractive alternative for fast and efficient differentiation of reducing and nonreducing carbohydrates, and the positions of nonreducing monosaccharide residues in a carbohydrate chain could be easily speculated. Copyright © 2013 John Wiley & Sons, Ltd.     

SDS/Ac2O/H2O: Surfactant‐Mediated Cleavage of Imines with Acetic Anhydride to Carbonyls and Acetanilides in Water

Surfactant (SDS)‐mediated cleavage of imines was achieved with acetic anhydride to the corresponding carbonyls (aldehydes and ketones) and acetanilides in water at 25–30°C with very good to excellent yields, thus contributing significantly to the green chemistry concept.     

Facile Synthesis and Unusual Methanesulfonylation Reaction of (2R,3R)‐1,4‐Dimethoxy‐1,1,4,4‐tetrasubstituted‐2,3‐butanediols

A facile method for the synthesis of (2R,3R)‐1,4‐dimethoxy‐1,1,4,4‐tetrasubstituted‐2,3‐butanediols involving oxidative cleavage of benzylidene acetal as a key step is described. These sterically hindered diols unusually formed cyclic sulfites as the major product under methanesulfonylation reaction conditions.     

两个带呋喃悬臂不对称大环双核铜配合物的合成、结构及性质

合成并表征了2个不对称大环双核铜配合物[Cu₂（L¹）Cl₂]·CH₃CN（1）和[Cu₂（L²）Br₂]·CH₃CN·H₂O（2）。配合物与CT-DNA的作用通过紫外-可见光谱,粘度实验,圆二色谱和凝胶电泳实验进行了研究。紫外-可见光谱的结果表明配合物与DNA的结合常数分别为6.2×10⁵和7.2×10⁵,圆二色谱的实验表明配合物能与DNA较好的结合,粘度实验表明配合物与DNA的结合为非典型的插入模式,凝胶电泳实验显示配合物通过氧化机理对DNA有较强的切割活性。