Ueber die Nachweisung des Holzgeistes

Ohne Zusammenfassung     

Rational Perturbation of the Fluorescence Quantum Yield in Emission‐Tunable and Predictable Fluorophores (Seoul‐Fluors) by a Facile Synthetic Method Involving CH Activation

Fluorescence imaging enables the uniquely sensitive observation of functional‐ and molecular‐recognition events in living cells. However, only a limited range of biological processes have been subjected to imaging because of the lack of a design strategy and difficulties in the synthesis of biosensors. Herein, we report a facile synthesis of emission‐tunable and predictable Seoul‐Fluors, 9‐aryl‐1,2‐dihydrolopyrrolo[3,4‐b]indolizin‐3‐ones, with various R¹ and R² substituents by coinage‐metal‐catalyzed intramolecular 1,3‐dipolar cycloaddition and subsequent palladium‐mediated C? H activation. We also showed that the quantum yields of Seoul‐Fluors are controlled by the electronic nature of the substituents, which influences the extent of photoinduced electron transfer. On the basis of this understanding, we demonstrated our design strategy by the development of a Seoul‐Fluor‐based chemosensor 20 for reactive oxygen species that was not accessible by a previous synthetic route.     

A New Sesquiterpene, α‐Santalane‐11,12,13‐Triol from the Root Bark of Severinia Buxifolia in Hainan

Anew sesquiterpenoid, α‐santalane‐11,12,13‐triol, together with thirty known compounds were isolated and characterized from the root bark of Severinia buxifolia in Hainan. Their structures were determined by spectroscopic methods. The relationship between constituents and collecting area is also discussed.     

A new convenient method for the synthesis of 2H‐1,4‐benzoxazine derivatives from nitroketones via intramolecular reductive cyclization

Dedicated to Professor Herbert C. Brown on the occasion of his 90^th birthday. Potentially bioactive 2H‐1,4‐benzoxazine derivatives could be conveniently prepared in one step from the corresponding nitroketones using 10% palladium on carbon with triethylamine in the presence of hydrogen (Pd/C‐TEA‐H₂) system. Several other tertiary amines such as nicotine, pyridine, and quinoline also could be used, but TEA gave the best results.     

The Law of the Iterated Logarithm for the Total Length of the Nearest Neighbor Graph

Let be the Poisson point process with intensity 1 in [–n,n] ^d . We prove the law of the iterated logarithm for the total length of the nearest neighbor graph on .     

Iron Porphyrins Embedded into a Supramolecular Porous Organic Cage for Electrochemical CO2 Reduction in Water

A porous organic cage composed of six iron tetraphenylporphyrins was used as a supramolecular catalyst for electrochemical CO₂‐to‐CO conversion. This strategy enhances active site exposure and substrate diffusion relative to the monomeric catalyst, resulting in CO generation with near‐quantitative Faradaic efficiency in pH 7.3 water, with activities reaching 55 250 turnovers. These results provide a starting point for the design of supramolecular catalysts that can exploit the properties of the surrounding matrix yet retain the tunability of the original molecular unit.     

Determination of trace and toxic elements in Korean rice CRM by INAA, ICP and AAS

Trace and toxic elements in Certified Reference Material (CRM) made of Korean rice at the Korea Research Institute of Standards and Science have been analyzed by Instrumental Neutron Activation Analysis (INAA). Data intercomparison from the measurement with those of Atomic Absorption Spectrometry (AAS) and Induced Coupled Plasma Spectrometry (ICPS) has been studied. The powdered samples were sterilized at 1.5·10⁶ rad in the bottles using a⁶⁰Co source after sieving and spiking to specific elements such as As, Cd, Cr, Cu and Hg and then the homogeneity of samples was assessed. Rice flour (SRM 1568a) and standard solutions made by the National Institute of Standards Technology (NIST) were used to construct the calibration curves for the INAA and the chemical methods, respectively. The uncertainties and concentration of constituent elements were determined and the possibility of their use for analytical quality control was considered.     

Molecular Modeling of Steroid–Nucleoside Conjugates: A Preliminary Structural Study

In recent years, molecular modeling has been used to predict structure and chemical behavior of molecules in order to design drugs and enhance the performance of pharmaceuticals. The size and complexity of molecules studied computationally has grown as the computational power available has increased, along with the creation and formulation of new theories and methods. We will apply these methods to a unique set of steroid-nucleoside conjugates in order to interpret their differences in activity. In the set of four studied in this work (three acids bonded to AZT through an ester bond and an additional isomer of the second in the series), only the cholenic acid-conjugated species (Conjugate 1) has exhibited antitumor behavior, while the other two, P-16-acid and P-21-oic acid (prednisolone with an ester linkage to zidovudine, AZT), do not. In this study, we use molecular mechanics and semiempirical techniques to compare structures and to examine rotational barriers and solvation effects on many of the low-lying conformations of these four conjugates, as well as to use electrostatic potential isosurfaces in order to gain insight into the contributions to the activity or inactivity of these potential antitumor drugs.     

A Cyclized Helix‐Loop‐Helix Peptide as a Molecular Scaffold for the Design of Inhibitors of Intracellular Protein–Protein Interactions by Epitope and Arginine Grafting

The design of inhibitors of intracellular protein–protein interactions (PPIs) remains a challenge in chemical biology and drug discovery. We propose a cyclized helix‐loop‐helix (cHLH) peptide as a scaffold for generating cell‐permeable PPI inhibitors through bifunctional grafting: epitope grafting to provide binding activity, and arginine grafting to endow cell‐permeability. To inhibit p53–HDM2 interactions, the p53 epitope was grafted onto the C‐terminal helix and six Arg residues were grafted onto another helix. The designed peptide cHLHp53‐R showed high inhibitory activity for this interaction, and computational analysis suggested a binding mode for HDM2. Confocal microscopy of cells treated with fluorescently labeled cHLHp53‐R revealed cell membrane penetration and cytosolic localization. The peptide inhibited the growth of HCT116 and LnCap cancer cells. This strategy of bifunctional grafting onto a well‐structured peptide scaffold could facilitate the generation of inhibitors for intracellular PPIs.