Surfactant displacement of human serum albumin adsorbed on loosely packed self-assembled monolayers: cetyltrimethylammonium bromide versus sodium dodecyl sulfate

The surfactants sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) displace human serum albumin (HSA) from loosely packed self-assembled monolayers (SAM) of hydrophobic alkyl chains by different means. Removal of HSA is of interest because previous work has suggested that the adsorption of HSA to such loosely packed SAMs may be sufficiently tenacious to offer opportunities for surface passivation. While HSA remains on the surface after exposure to SDS and rinsing, no protein remains after exposure to CTAB and rinsing. X-ray reflectivity and X-ray photoelectron spectroscopy measurements indicate that CTAB molecules remain interdigitated in the loosely packed SAM after rinsing, suggesting that CTAB is more effective in removing the HSA because it interacts more strongly with the SAM.     

Probing metabolic alterations in breast cancer in response to molecular inhibitors with Raman spectroscopy and validated with mass spectrometry

Rapid and accurate response to targeted therapies is critical to differentiate tumors that are resistant to treatment early in the regimen. In this work, we demonstrate a rapid, noninvasive, and label-free approach to evaluate treatment response to molecular inhibitors in breast cancer (BC) cells with Raman spectroscopy (RS). Metabolic reprogramming in BC was probed with RS and multivariate analysis was applied to classify the cells into responsive or nonresponsive groups as a function of drug dosage, drug type, and cell type. Metabolites identified with RS were then validated with mass spectrometry (MS). We treated triple-negative BC cells with Trametinib, an inhibitor of the extracellular-signal-regulated kinase (ERK) pathway. Changes measured with both RS and MS corresponding to membrane phospholipids, amino acids, lipids and fatty acids indicated that these BC cells were responsive to treatment. Comparatively, minimal metabolic changes were observed post-treatment with Alpelisib, an inhibitor of the mammalian target of rapamycin (mTOR) pathway, indicating treatment resistance. These findings were corroborated with cell viability assay and immunoblotting. We also showed estrogen receptor-positive MCF-7 cells were nonresponsive to Trametinib with minimal metabolic and viability changes. Our findings support that oncometabolites identified with RS will ultimately enable rapid drug screening in patients ensuring patients receive the most effective treatment at the earliest time point.

Rapid and accurate response to targeted therapies is critical to differentiate tumors that are resistant to treatment early in the regimen.     

Nonlinear electrokinetics and "superfast" electrophoresis

Nonlinear and nonequilibrium electrophoresis of spherical particles of radius a is shown to be possible when the solid surface allows field or current penetration. At low particle Peclet numbers, transient capacitative charging occurs until the surface polarization completely screens the external field. For a DC applied field [see text], the resulting electrokinetic velocity reaches Dukhin's maximum value of [formula: see text], where [see text] and mu are the liquid permittivity and viscosity. At high Peclet numbers, electroosmotic convection of the electroneutral bulk stops the transient charging before complete field-line exclusion. For an ion-selective and conducting spherical granule, the polarization is then determined by the steady-state Ohmic current driven by the penetrated external field. The high-Peclet electrokinetic velocity is lower, diffusivity-dependent and scales as [see text].     

Two-Photon Excitation of 4'-Hydroxymethyl-4,5',8-Trimethylpsoralen

Abstract— Psoralens are a class of pharmaceutical agents commonly used to treat several cutaneous disorders. When irradiated with a mode-locked titanium: sapphire (Ti: sapphire) laser tuned to 730 nm, an aqueous solution of 4'-hydroxymethyl-4,5',8-trimethylpsoralen (HMT) emits blue light. The emission spectrum is centered at 452 nm and is identical to that obtained by one-photon excitation with UVA excitation, and its magnitude depends quad-ratically on the intensity of laser excitation. These results suggest that two-photon excitation occurs to a potentially photochemically active state. To estimate the two-photon absorption cross section, it was first necessary to measure the emission quantum yield of HMT using 365 nm excitation at room temperature that resulted in a value of 0.045 ± 0.007. The two-photon absorption cross section of HMT at 730 nm is therefore estimated to be 20 ± 10⁻⁵⁰ cm⁴ s (20 Göppert-Mayer). The excited-state photophysics and photochemistry of psoralens suggest potential applications to cutaneous phototherapy in diseases such as psoriasis and dystrophic epidermolysis bullosa.     

Interfacial micellar structures from novel amphiphilic star polymers

An amphiphilic heteroarm star polymer containing 12 alternating hydrophobic/hydrophilic arms of polystyrene (PS) and poly(acrylic acid) (PAA) connected to a well-defined rigid aromatic core was studied at the air-water and the air-solid interfaces. At the air-water interface, the molecules spontaneously form pancakelike micellar aggregates which measure up to several microns in diameter and 5 nm in thickness. Upon reduction of the surface area per molecule to 7 nm2, the two-dimensional micelles merged into a dense monolayer. We suggest that confined phase separation of dissimilar polymer arms occurred upon their segregation on the opposite sides of the rigid disklike aromatic core, forcing the rigid cores to adopt a face-on orientation with respect to the interface. Upon transfer onto solid supports the PS chains face the air-film interface making it completely hydrophobic, and the PAA chains were found to collapse and form a thin flattened underlayer. This study points toward new strategies to create large 2D microstructures with facial amphiphilicity and suggests a profound influence of star molecular architecture on the self-assembly of amphiphiles at the air-water interface.     

Estimation of the absolute internal-rotation entropy of molecules with two torsional degrees of freedom from stochastic simulations

A method of statistical estimation is applied to the problem of evaluating the absolute entropy of internal rotation in a molecule with two torsional degrees of freedom. The configurational part of the entropy is obtained as that of the joint probability density of an arbitrary form represented by a two-dimensional Fourier series, the coefficients of which are statistically estimated using a sample of the torsional angles of the molecule obtained by a stochastic simulation. The internal rotors in the molecule are assumed to be attached to a common frame, and their reduced moments of inertia are initially calculated as functions of the two torsional angles, but averaged over all the remaining internal degrees of freedom using the stochastic-simulation sample of the atomic configurations of the molecule. The torsional-angle dependence of the reduced moments of inertia can be also averaged out, and the absolute internal-rotation entropy of the molecule is obtained in a good approximation as the sum of the configurational entropy and a kinetic contribution fully determined by the averaged reduced moments of inertia. The method is illustrated using Monte Carlo simulations of isomers of stilbene and halogenated derivatives of propane. The two torsional angles in cis-stilbene are found to be much more strongly correlated than those in trans-stilbene, while the degree of the angular correlation in propane increases strongly on substitution of hydrogen atoms with chlorine.     

On the red shift of OH stretching region vibrations in ice and water

The nature of the red shift of frequencies of the fundamental modes, v₁ and v₃, in the OH stretching region of the vibrational spectrum of ice (and, possibly, in water) under H-bonding formation is explained in the framework of the continuum approach for the one-dimensional infinite chain of water molecules represented as dipolar and polarizable OH oscillators vibrating in the definite force field. The explicit expressions in the form of the generalized cnoidal nonlinear waves describing these fundamental modes and obtained as the solutions of the nonlinear Klein–Gordon equation of motion, and their red shifts that are consistent with experimental observations, are presented.     

Beiträge zur Chemie der Silicium—Stickstoff-Verbindungen, 21. Mitt.

Zusammenfassung Durch Umsetzung von Disilbercyanamid mit Organyl- und Alkoxy-halogensilanen wurden 9 bisher unbekannte zweifach silylsubstituierte Carbodiimide der Stoffgruppen (R₃SiN)₂C, [(RO)₃SiN]₂C, (R₂RSiN)₂C und R₃SiNCNSiR₃ dargestellt und in ihrer Struktur über¹⁴N- und¹H-kernmagnetische Resonanzmessungen, IR- und Raman-Spektren eindeutig als Carbodiimidderivate aufgeklärt.20. Mitt.:U. Wannagat undH. Kuckertz, Angew. Chem.75, 95 (1963).Zugleich 2. Mitt. über silylsubstituierte Carbodiimide; 1. Mitt.J. Pump undU. Wannagat, Ann. Chem.652, 21 (1962); Angew. Chem.74, 117 (1962); Österr. Chemiker-Ztg.62, 319 (1961).     

Synthesis and pharmacological evaluation of new 16-methyl pregnane derivatives

The pharmacological activity of several new pregnane derivatives 15-19 were determined on gonadectomized male hamster flank organs, seminal vesicles and in vitro conversion of testosterone (T) to dihydrotestosterone (DHT) as 5alpha-reductase inhibitors. Steroids 15-19 decreased the diameter of the pigmented spot in the flank organs as compared to the T treated animals; in this model, steroids 16 and 19 showed a higher activity than the commercially available finasteride 3. Injection of T increased the weight of the seminal vesicles. Compounds 15-19 when injected together with T decreased the weight of the seminal vesicles thus showing an antiandrogenic effect. The trienone 19 exhibited a considerably higher activity than finasteride. Steroids 15-19 inhibited the in vitro metabolism of [3H]T to [3H]DHT in seminal vesicles homogenates of gonadectomized male hamsters. Compounds 18 and 19 showed a much higher antiandrogenic effect than finasteride. This enhancement of the biological activity could probably be attributed to the coplanarity of the steroidal skeleton as previously observed by our group. The high antiandrogenic activity of the epoxy compound 16 is probably the result of the ring opening of the oxiran ring with the nucleophilic part of the enzyme 5alpha-reductase thus leading to a stable adduct with concomitant deactivation of this enzyme.     

Electron transfer in the reduction of primary halides by metal hydrides

The reactions of various main-group metal hydrides with 1-halo-5-hexenes and with 1-halo-2,2-dlmethyl-5-hexenes produce both straight chain and cyclized reduction products. The formation of cyclic hydrocarbons clearly indicates the presence of radical intermediates during the course of these reactions.