Hybridization and Melting Behavior of Peptide Nucleic Acid (PNA) Oligonucleotide Chimeras Conjugated to Gold Nanoparticles

Peptide nucleic acids (PNA) and PNA–DNA chimeras carrying thiol groups were used for surface functionalization of Au nanoparticles. Conjugation of PNA to citrate‐stabilized Au nanoparticles destabilized the nanoparticles causing them to precipitate. Addition of a tail of glutamic acid to the PNA prevented destabilization of the nanoparticles but resulted in loss of interaction with complementary sequences. Importantly, PNA–DNA chimeras gave stable conjugates with Au nanoparticles. The hybridization and melting properties of complexes formed from chimera–nanoparticle conjugates and oligonucleotide–nanoparticle conjugates are described for the first time. Similar to oligonucleotide–nanoparticle conjugates, conjugates with PNA–DNA chimeras gave sharper and more‐defined melting profiles than those obtained with unmodified oligonucleotides. In addition, mismatch discrimination was found to be more efficient than with unmodified oligonucleotides.     

Loss of H2O from M + t-Butyl Complex Ions of Benzyl Alcohol in Isobutane Chemical Ionization Mass Spectrometry

In isobutane chemical ionization mass spectrometry benzyl alcohol exhibits ions at m/z 147 (‘M + 39’) that arise by a loss of H₂O from [M + C₄H₉]⁺, i.e. ‘M + 57’ complex ions. Electrophilic aromatic substitution of a proton at an ortho-position of neutral C₆H₅CH₂OH with [t-C₄H₉]⁺ and, alternatively, nucleophilic substitution of H₂O at the benzylic carbon in \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm C_6 H_5 CH_2}\mathop {\rm O}\limits^+ {\rm H}_2 $\end{document} with CH₂?C (CH₃)₂ are discussed as possible pathways. Evidence in favor of the latter is derived from the analysis of C₆D₅CH₂OH and C₆H₅CD₂OH for the origin of the H-atoms lost in H₂O. The inferred ion structure of m/z 147 is verified by mass-analyzed ion kinetic energy (MIKE.) measurements of its collision-activated (CA.) decomposition. MIKE./CA. spectra of mass-selected m/z 147 ions, once generated by (CI(i-C₄H₁₀) from benzyl alcohol and, once, from 2-methyl-4-phenyl-2-butanol match closely and, thus, reflect identical ion structures. With reference to the simple genesis of this ion from the latter precursor, the structure in question can be concluded to be \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm C_6 H_5 CH_2 CH_2}\mathop {\rm C}\limits^+ ({\rm CH}_3)_2 $\end{document} .     

Bimetallic Gold(I) Complexes with Ethynyl‐Helicene and Bis‐Phosphole Ligands: Understanding the Role of Aurophilic Interactions in their Chiroptical Properties

Monometallic gold(I)‐alkynyl‐helicene complexes ( 1 a , b ) and bimetallic gold(I)‐alkynyl‐helicene architectures featuring the presence ( 2 a , b ) or absence ( 3 a , b ) of aurophilic intramolecular interactions were prepared by using different types of phosphole ligands (mono‐phosphole L1 or bis‐phospholes L2 , 3 ). The influence of the Au^I d¹⁰ metal center(s) on the electronic, photophysical, and chiroptical properties of these unprecedented phosphole‐gold(I)‐alkynyl‐helicene complexes was examined. Experimental and theoretical results highlight the importance of ligand‐to‐ligand‐type charge transfers and the strong effect of the presence or absence of Au^I–Au^I interactions in 2 a , b .     

Superstructure in chemically etched poly(ethylene terephthalate)

The new technique of contact etching has been utilized to study the bulk morphology of polyethylene terephthalate by the echant, n-propylamine. A variety of films and fibers with different mechanical and thermal histories have been subjected to contact etching. The sample surfaces have been studied principally by scanning electron microscopy. A network superstructure with its characteristic dimension (thickness) of from 700 to 3000 Å, depending on sample history, has been observed. In the oriented samples the network superstructure aligns perpendicular to the direction of sample orientation. A simple model is proposed to describe the network superstructure which is believed to be moderately crystalline.     

Synthesis of Ajoene Analogues by Novel Synthetic Strategies

Ajoene is a compound found in garlic extracts exhibiting a large range of biological activity. Novel ajoene analogues have been prepared in the search of compounds with superior bioactivity. Modifications include the alteration of the sulfoxide, the central alkene and the terminal allyl groups.     

Synthesis of Novel Unsymmetrical and Symmetrical Diacetylenic Ketones

A convenient and efficient method for the preparation of unsymmetrical and symmetrical diacetylenic ketones bearing a carboxylate group.     

Heat capacity of the white pine biocarbon preform and the related biocarbon/copper composite

This paper reports on measurements in the 80–300-K temperature interval of the heat capacity at constant pressure C _p (T) of high-porosity amorphous white pine carbon preforms (biocarbon) prepared by pyrolysis (carbonization) at T _carb = 1000 and 2400°C in an argon flow. The dependences C _p (T) for biocarbon/copper composites based on the carbon preforms obtained have also been determined. It is shown that the mixture rule holds for the composites, i.e., that C _p (T) of the composite is a sum of the heat capacities of the constituent materials taken in the corresponding ratios. Phonon mean free paths for the white pine carbon preforms prepared at T _carb = 1000 and 2400°C have been calculated and used to estimate the size of the nanocrystallites contributing to formation of the carbon frameworks of these preforms.