Photo-triggered generation of a free thiol group on DNA: application to DNA conjugation

DNA oligomers possessing a 2-nitrobenzyl (NB) protected thiol group have been prepared. The photo-remove of the NB to generate a free thiol group in DNA has been analyzed by using reverse-phase HPLC and denaturing gel electrophoresis. The photo-triggered generation of the thiol function in DNA was applicable in the light-initiated ligation of thiol-modified DNA oligomers and Au–DNA conjugation.     

Measurement of excitation-contraction coupling time in lower extremities

Objective: The aim of this study was to apply a novel method to measure excitation-contraction coupling time (ECCT) in normal soleus muscles. Methods: We performed simultaneous recordings of soleus compound muscle action potential (CMAP) and foot movement-related potential (MRP), and measured ankle plantar flexion torque in 36 healthy subjects. We calculated ECCT and examined the relations between CMAP, MRP, ECCT and ankle plantar flexion torque. Results: Statistical analyses established reference ranges (mean ± SE) for CMAP (13.4 ± 0.9 mV), MRP (5.3 ± 0.4 m/s²), ECCT (5.2 ± 0.1 ms), torque (85.9 ± 6.4 Nm) and torque/body weight (1.4 ± 0.1 Nm/kg). The torque showed a positive linear correlation with CMAP (p = 0.041) and a negative linear correlation with ECCT (p = 0.045). Conclusion: Soleus ECCT can be recorded easily, and is useful to assess the impairment of E-C coupling in muscles of the lower extremities.     

Helical Oligoenes: Conformations,Bond Alternation,and Competing Through‐Bond and Through‐Space Transmission

There is a consensus that long‐range electron transfer/transport occurs by a through‐bond rather than through‐space mechanism. In helical all‐Z, all‐s‐cis oligoenes, one can set up an interesting competition in the medium‐separation regime between a closer (in distance) through‐space path and a more distant through‐bond one. Although such oligoene conformations/isomers are unstable (by around 4 kcal mol^?1 per double bond relative to all‐E, all‐s‐trans isomers), recent synthetic efforts on truncated helicenes and oligothiophenes have provided related molecules. On the way to transmission calculations with electrodes attached to the termini of helical oligoenes, we uncover an interesting conformational ambiguity in all‐Z, all‐s‐cis oligoenes, the existence of a broad conformational minimum for helical compression, with hints of end‐to‐end frontier‐orbital‐caused stabilization. There is relationship between helical oligoene structures and the corresponding substructure of a helicene, but there are also significant differences in the number of olefin subunits per helix turn. In Hückel transport calculations, the role of TB or TS mechanisms is obscured to an extent by variations in bond alternation and dihedral angle along the oligomer chain. However, the operation of a dominant through bond mechanism emerges clearly in local transmission plots. In moving the electrodes to carbon position related by quantum interference, it is possible to uncover a through space mechanism.     

Promotion of Double‐Duplex Invasion of Peptide Nucleic Acids through Conjugation with Nuclear Localization Signal Peptide

Pseudo‐complementary peptide nucleic acid (pcPNA), as one of the most widely used synthetic DNA analogues, invades double‐stranded DNA according to Watson–Crick rules to form invasion complexes. This unique mode of DNA recognition induces structural changes at the invasion site and can be used for a range of applications. In this paper, pcPNA is conjugated with a nuclear localization signal (NLS) peptide, and its invading activity is notably promoted both thermodynamically and kinetically. Thus, the double‐duplex invasion complex is formed promptly at low pcPNA concentrations under high salt conditions, where the invasion otherwise never occurs. Furthermore, NLS‐modified pcPNA is successfully employed for site‐selective DNA scission, and the targeted DNA is selectively cleaved under conditions that are not conducive for DNA cutters using unmodified pcPNAs. This strategy of pcPNA modification is expected to be advantageous and promising for a range of in vitro and in vivo applications.     

Design and Synthesis of Glycosylated Cholera Toxin B Subunit as a Tracer of Glycoprotein Trafficking in Organelles of Living Cells

Glycosylation of proteins is known to be essential for changing biological activity and stability of glycoproteins on the cell surfaces and in body fluids. Delivering of homogeneous glycoproteins into the endoplasmic reticulum (ER) and the Golgi apparatus would enable us to investigate the function of asparagine-linked (N-) glycans in the organelles. In this work, we designed and synthesized an intentionally glycosylated cholera toxin B-subunit (CTB) to be transported to the organelles of mammalian cells. The heptasaccharide, the intermediate structure of various complex-type N-glycans, was introduced to the CTB. The synthesized monomeric glycosyl-CTB successfully entered mammalian cells and was transported to the Golgi and the ER, suggesting the potential use of synthetic CTB to deliver and investigate the functions of homogeneous N-glycans in specific organelles of living cells.     

Excitation-Wavelength-Dependent Functionalities of Temporally Controlled Sensing and Generation of Singlet Oxygen by a Photoexcited State Engineered Rhodamine 6G-Anthracene Conjugate

The present study provides design guidance for unique multipotent molecules that sense and generate singlet oxygen (¹O₂). A rhodamine 6G-aminomethylanthracene-linked donor-acceptor molecule ( RA ) is designed and synthesized for demonstrating wavelength-dependent functionalities as follows; (i) RA acts as a conventional fluorogenic ¹O₂ sensor molecule like the commercially available reagent, singlet oxygen sensor green (SOSG), when it absorbs ultraviolet (UV)-visible light and reacts with ¹O₂. (ii) RA acts as a temporally controlled ¹O₂ sensing reagent under the longer wavelength (∼700 nm) photosensitization. RA enters an intermediate state after capturing ¹O₂ and does not become strongly fluorescent until it is exposed to UV, blue, or green light. (iii) RA acts as an efficient photosensitizer to generate ¹O₂ under green light illumination. The spin-orbit charge transfer mediated intersystem crossing (SOCT-ISC) process achieves this function, and RA shows a potential cancer-killing effect on pancreatic cancer cells. The wavelength-switchable functionalities in RA offer to promise molecular tools to apply ¹O₂ in a spatiotemporal manner.     

Fragmentation of tertiary cyclopropanol compounds catalyzed by vanadyl acetylacetonate

Tertiary cyclopropanol compounds react with a catalytic amount of vanadyl acetylacetonate in the presence of oxygen affording β-hydroxyketones and β-diketones. For 3-substituted-bicyclo[4.1.0]alkanols, peroxides are obtained, as are the β-hydroxyketones. Conversely, 2-ethoxycarbonylcyclopropyl silyl ethers produce ethyl γ-oxocarboxylate derivatives given the same reaction conditions.