Cytotoxic Coumarins from the Bark of Mammea siamensis

A new geranylated coumarin, (E)-4-(1-hydroxypropyl)-5,7-dihydroxy-6-(3,7-dimethyl-2,6-octadienyl)-8-(3-methyl-1-oxobutyl)coumarin (named surangin D), was isolated from the bark of Mammea siamensis collected in Vietnam, along with four known coumarins, surangins B and C, and theraphins B and C, and seven xanthones, 1,7-dihydroxyxanthone, 7-hydroxy-1-methoxyxanthone, 1,7-dimethoxyxanthone, 1,7-dimethoxy-6-hydroxyxanthone, 1,6,7-trihydroxyxanthone, 1,3,7-trihydroxyxanthone, and 1,7-dihydroxy-3-methoxyxanthone. Their structures were determined by spectroscopic methods (mainly 1D- and 2D-NMR) and preparation of methylated derivatives. The four coumarins, surangins C and D and theraphins B and C, were tested for inhibition of cell proliferation in DLD-1 (colon cancer), MCF-7 (breast adenocarcinoma), HeLa (human cervical cancer) and NCI-H460 (human lung cancer) cell lines using the sulforhodamine B (SRB) assay. In all four cell lines, theraphin C showed the strongest activity (IC?? in the range of 1.6-5.7 μM). Testing the anti-proliferative effect of the methylated derivatives showed reduced cellular effects of all derivatives, indicating that the number and position of free hydroxyl groups were very important for the anti-proliferative effect.     

Corrigendum to: “Fractional Functional Differential Inclusions with Finite Delay” [Nonlinear Anal. 70(5) (2009) 2091–2105]

We correct an error made in the paper (J. Henderson and A. Ouahab, Fractional Functional Differential Inclusions with Finite Delay [Nonlinear Anal. 70(5) (2009) 2091–2015]), in an application of Theorem 4.1 in the proof of Theorem 4.2. We have revised the statement of Theorem 4.2 so that Theorem 4.1 is now applicable in its proof.     

Catalytic Transfer Deuteration and Hydrodeuteration: Emerging Techniques to Selectively Transform Alkenes and Alkynes to Deuterated Alkanes

Increasing demand for deuterium-labeled organic molecules has spurred a renewed interest in selective methods for deuterium installation. Catalytic transfer deuteration and transfer hydrodeuteration are emerging as powerful techniques for the selective incorporation of deuterium into small molecules. These reactions not only obviate the use of D₂ gas and pressurized reaction setups but provide new opportunities for selectively installing deuterium into small molecules. Commercial or readily synthesized deuterium donors are typically employed as easy-to-handle reagents for transfer deuteration and hydrodeuteration reactions. In this minireview, recent advances in the catalytic transfer deuteration and hydrodeuteration of alkenes and alkynes for the selective synthesis of deuterated alkanes will be discussed.     

Determination of Internal Energy Distributions of Laser Electrospray Mass Spectrometry using Thermometer Ions and Other Biomolecules

The internal energy distributions for dried and liquid samples that were vaporized with femtosecond duration laser pulses centered at 800 nm and postionized by electrospray ionization-mass spectrometry (LEMS) were measured and compared with conventional electrospray ionization mass spectrometry (ESI-MS). The internal energies of the mass spectral techniques were determined by plotting the ratio of the intact parent molecular features to all integrated ion intensities of the fragments as a function of collisional energy using benzylpyridinium salts and peptides. Measurements of dried p-substituted benzylpyridinium salts using LEMS resulted in a greater extent of fragmentation in addition to the benzyl cation. The mean relative internal energies, int> were determined to be 1.62?±?0.06, 2.0?±?0.5, and 1.6?±?0.3 eV for ESI-MS, dried LEMS, and liquid LEMS studies, respectively. Two-photon resonances with the laser pulses likely caused lower survival yields in LEMS analyses of dried samples but not liquid samples. In studies with larger biomolecules, LEMS analyses of dried samples from glass showed a decrease in survival yield compared with conventional ESI-MS for leucine enkephalin and bradykinin of ~15% and 11%, respectively. The survival yields for liquid LEMS analyses were comparable to or better than ESI-MS for benzylpyridinium salts and large biomolecules. Figure

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Impulsive neutral functional differential equations in banach spaces

In this paper, a fixed point theorem due to Schaefer is used to investigate the existence of solutions for first and second order impulsive neutral functional differential equations in Banach spaces.     

Vapor pressure and density of thermotropic liquid crystals: MBBA, 5CB, and novel fluorinated mesogens

The vapor pressures and densities of six thermotropic liquid crystal-forming molecules (mesogens) have been determined experimentally as functions of temperature. The ubiquitous mesogenic compounds n-(4-methoxybenzylidene)-4-butylaniline (MBBA) and 4'-cyano-4-n-pentylbiphenyl (5CB), which both exhibit room-temperature nematic phases, are examined in this study, as are a number of trifluorinated bicyclohexyl and cyclohexylbiphenyl derivatives which find modern use in display applications. Although thermotropic mesogens are of prime importance in modern optoelectronic technologies, there is a scarcity of reliable saturation pressure data for such systems. An apparatus suitable for measurements of vapor pressures between 0.1 and 1333 Pa in the temperature range 298-523 K has been constructed. The adequacy of the apparatus has been verified by measurements on n-hexadecane at temperatures between 304 and 372 K, corresponding to vapor pressures between 0.4 and approximately 100 Pa. To our knowledge, our measurements represent the first reliable data for the saturation pressure of the fluid phase of these types of thermotropic compounds; we show that existing data for MBBA is thermodynamically inconsistent. The densities of the fluid phases of these compounds are also measured by means of a glass pycnometer at temperatures between 293 and 368 K.     

Dynamic boundary value problems of the second-order: Bernstein–Nagumo conditions and solvability

This article analyzes the solvability of second-order, nonlinear dynamic boundary value problems (BVPs) on time scales. New Bernstein–Nagumo conditions are developed that guarantee an a priori bound on the delta derivative of potential solutions to the BVPs under consideration. Topological methods are then employed to gain solvability.     

Highly Selective Lysine Acylation in Proteins Using a Lys-His Tag Sequence

Chemical modification of proteins has numerous applications, but it has been challenging to achieve the required high degree of selectivity on lysine amino groups. Recently, we described the highly selective acylation of proteins with an N-terminal Gly-His₆ segment. This tag promoted acylation of the N-terminal N^α-amine resulting in stable conjugates. Herein, we report the peptide sequences His_n-Lys-His_m, which we term Lys-His tags. In combination with simple acylating agents, they facilitate the acylation of the designated Lys N^ϵ-amine under mild conditions and with high selectivity over native Lys residues. We show that the Lys-His tags, which are 7 to 10 amino acids in length and still act as conventional His tags, can be inserted in proteins at the C-terminus or in loops, thus providing high flexibility regarding the site of modification. Finally, the selective and efficient acylation of the therapeutic antibody Rituximab, pure or mixed with other proteins, demonstrates the scope of the Lys-His tag acylation method.     

A Bis-Acridinium Macrocycle as Multi-Responsive Receptor and Selective Phase-Transfer Agent of Perylene

A bis-acridinium cyclophane incorporating switchable acridinium moieties linked by a 3,5-dipyridylanisole spacer was studied as a multi-responsive host for polycyclic aromatic hydrocarbon guests. Complexation of perylene was shown to be the most effective and was characterized in particular by a charge-transfer band as signal output. Effective catch and release of the guest was triggered by both chemical (proton/hydroxide) and redox stimuli. Moreover, the dicationic host was also easily switched between organic and perfluorocarbon phases for applications related to the enrichment of perylene from a mixture of polycyclic aromatic hydrocarbons.     

Diastereo- and Enantioselective 1,4-Difunctionalization of Borylenynes by Catalytic Conjunctive Cross-Coupling

Enantioselective conjunctive cross-coupling of enyne-derived boronate complexes occurs with 1,4 addition of the electrophile and migrating group across the π system. This reaction pathway furnishes α-boryl allenes as the reaction product. In the presence of a chiral catalyst, both the central and axial chirality of the product can be controlled during product formation.