Rational designing of glyco-nanovehicles to target cellular heterogeneity

The aberrant expression of endocytic epidermal growth factor receptors (EGFRs) in cancer cells has emerged as a key target for therapeutic intervention. Here, we describe for the first time a state-of-the-art design for a heparan sulfate (HS) oligosaccharide-based nanovehicle to target EGFR-overexpressed cancer cells in cellular heterogeneity. An ELISA plate IC₅₀ inhibition assay and surface plasma resonance (SPR) binding assay of structurally well-defined HS oligosaccharides showed that 6-O-sulfation (6-O-S) and 6-O-phosphorylation (6-O-P) of HS tetrasaccharides significantly enhanced EGFR cognate growth factor binding. The conjugation of these HS ligands to multivalent fluorescent gold nanoparticles (AuNPs) enabled the specific and efficient targeting of EGFR-overexpressed cancer cells. In addition, this heparinoid-nanovehicle exhibited selective homing to NPs in cancer cells in three-dimensional (3D) coculture spheroids, thus providing a novel target for cancer therapy and diagnostics in the tumor microenvironment (TME).

Heparan sulfate oligosaccharide based nanovehicle greatly enhance the selective targeting of cancer cells in tumor microenvironment.     

Synthesis and characterization of 4-dimethylamino-N-triphenylmethylpyridinium chloride,a postulated intermediate in the tritylation of alcohols

4-Dimethylamino-$\text{N}$-triphenylmethylpyridinium chloride ($\text{1}$) reacts with primary but not secondary alcohols to produce trityl ethers in good yield; in addition, amines may be selectively $\text{N}$- tritylated witth $\text{1}$ in the presence of alcohols.     

19-electron intermediates and cage-effects in the photochemical disproportionation of [CpW(CO)3]2 with Lewis bases

The role of 19-electron intermediates in the photochemical disproportionation of [CpW(CO)3]2 (Cp = C5H5) with Lewis bases (PR3; R = OMe, Bu, Ph) is investigated on the ultrafast time scale using femtosecond VIS-pump, IR-probe spectroscopy. Formation of a 19-electron (19e) species CpW(CO)3PR3*by coordination of PR3 with photogenerated 17-electron (17e) radicals CpW(CO)3* is directly observed, and equilibrium is established between the 17e radicals and the 19e intermediates favoring 19e intermediates in the order: Bu > OMe > Ph. Steric effects dominate the 17e/19e equilibrium when the cone-angle of the Lewis base exceeds a certain limiting value (between 132 degrees and 145 degrees ), but below this value electronic properties of the Lewis base control the 17e/19e dynamics. Disproportionation occurs in less than 200 picoseconds by electron transfer between a solvent caged 17e radical and 19e, highly reducing species. The rate and extent of ultrafast disproportionation depends on both the identity and concentration of the Lewis base. In low concentrations of PR3 (typically 1-2 M or less) or with Lewis bases whose equilibrium heavily favors 17e radicals (e.g., PPh3), disproportionation is rate-limited by breakdown of the solvent cage. Density functional theory calculations on vibrational frequencies and charge distributions of the various complexes support the experimental results.     

Kinetic analysis of cyclic CMP-specific and multifunctional phosphodiesterases by quantitative positive-ion fast-atom bombardment mass spectrometry

Two enzymes, cyclic CMP-specific phosphodiesterase and multifunctional phosphodiesterase, are responsible for the hydrolysis of cytidine 3',5'-cyclic monophosphate in living cells. Quantitation of both enzymes has been carried out by positive-ion fast-atom bombardment mass spectrometric analysis of the enzyme incubates after termination of the reaction. The kinetic data obtained are in close agreement with parallel data obtained by the conventional radiometric assay. The extra facility of the mass spectrometry based assay to monitor several incubation components simultaneously has been exploited to study the concurrent hydrolysis of alternate cyclic nucleotide substrates and provides kinetic parameters of significance in interpreting substrate-enzyme interactions. This is extended by the use of collisionally-induced dissociation of the protonated molecules of the liberated products to identify the mononucleotide isomers resulting from the cyclic nucleotide hydrolysis.     

A finite element based algorithm for determining interfacial tension (gamma) from pendant drop profiles

This paper introduces a robust algorithm to determine the interfacial tension (gamma) from pendant drop profiles using the Galerkin finite element method (gamma-PD-FEM) to solve the axisymmetric form of the Young-Laplace (YL) equation. In this algorithm, the theoretical profiles are generated by solving the spherical coordinate form of the YL equation. gamma-PD-FEM also solves for the parameter estimates by minimizing the difference between the theoretical and experimental surface functions, f(theta). This technique is compared to the widely used method of converting the YL equation to the three arc length-based (ALB) first-order ODEs developed by Bashforth and Adams (BA) in 1883, or as denoted in this paper, the gamma-PD-BA method. The drop apex is the initial condition for the gamma-PD-BA algorithm and the integration is terminated at a specified location along the drop profile. In contrast to techniques based on the BA approach, computation of the theoretical drop profile in gamma-PD-FEM is obtained from a second-order ordinary differential equation and requires boundary conditions at the drop apex and at the contact line of the drop to the nozzle. By incorporating both boundary conditions into the problem formulation, the algorithm can also determine if the drop shape is at static equilibrium. Results to be presented include an outline of the computer algorithm, and comparison of gamma values obtained from the gamma-PD-FEM and the traditional gamma-PD-BA method using simulated and experimental drop profile data sets.     

Proton-transfer dynamics in the activation of cytochrome P450eryF

Molecular dynamics simulations are combined with quantum chemistry calculations of instantaneous proton-transfer energy profiles to investigate proton-transfer events in the transient pathway of cytochrome P450eryF (6-deoxyerythronolide B hydroxylase; CYP107A1), from the oxyferrous species to the catalytically active ferryl oxygen species (compound I). This reaction is one of the most fundamental unresolved aspects in the mechanism of oxidation that is common to all cytochrome P450s. We find that this process involves an ultrafast proton transfer from the crystallographic water molecule W519 to the distal oxygen bound to the heme group, and a subsequent proton-transfer event from W564 to W519. Both proton-transfer events are found to be endothermic in the oxyferrous state, suggesting that the oxyferrous reduction is mechanistically linked to the proton-transfer dynamics. These findings indicate that the hydrogen bond network, proximate to the O(2)-binding cleft, plays a crucial functional role in the enzymatic activation of P450s. Our results are consistent with the effect of mutations on the enzymatic efficacy.     

A robust algorithm for the simultaneous parameter estimation of interfacial tension and contact angle from sessile drop profiles

The pendant and sessile drop profile analysis using the finite element method (PSDA-FEM) is an algorithm which allows simultaneous determination of the interfacial tension (gamma) and contact angle (theta(c)) from sessile drop profiles. The PSDA-FEM algorithm solves the nonlinear second-order spherical coordinate form of the Young-Laplace equation. Thus, the boundary conditions at the drop apex and contact position of the drop with the substrate are required to solve for the drop profile coordinates. The boundary condition at the position where the drop contacts the substrate may be specified as a fixed contact line or fixed contact angle. This paper will focus on the fixed contact angle boundary condition for sessile drops on a substrate and how this boundary condition is used in the PSDA-FEM curve-fitting algorithm. The PSDA-FEM algorithm has been tested using simulated drop shapes with and without the addition of random error to the drop profile coordinates. The random error is varied to simulate the effect of camera resolution on the estimates of gamma and theta(c) values obtained from the curve-fitting algorithm. The error in the experimental values for gamma from sessile drops of water on acrylic and Mazola corn oil on acrylic falls within the predicted range of errors obtained for gamma values from simulated sessile drop profiles with randomized errors that are comparable in magnitude to the resolution of the experimental setup.     

Synthesis and electron impact mass spectra of 3-substituted 2-acylaminoindazoles

3-Substituted-2-acylaminoindazoles 2 were prepared via oxidative cyclization of o-aminoaryl ketone acylhydrazones 1 with iodosobenzene diacetate. Their electron ionization mass spectra were recorded and in addition to the molecular ions show common fragmentation pathways corresponding to the [M-N₂]⁺, [M-NHCOX]⁺ and [M-COX]⁺ ions, with some influence on the skeletal fragmentation by different substituents.     

Micellar solubilization: structural and conformational changes investigated by 1H and 13C liquid-state NMR

A combination of (1)H self-diffusion measurements and (13)C chemical shift analysis has been used for the study of the solubilization of amphiphilic additives C(n)H(2n+1)X (n=4, 6; X=OH, NH(2)) in cetyltrimethylammonium bromide (CTAB) micelles. This approach, which could be extended to other mixed systems, allows complementary data on structures of micelles and conformations of alkyl chains to be obtained. Previous results on these systems are confirmed and new features emerge. All the additives studied behave as cosurfactants. Their degree of solubilization is determined solely by their alkyl chain length. In the case of cosurfactants with n=6, polar head group differences have been shown to modify micellar structures. This effect has been linked to differences in cosurfactant penetration into micelles. In parallel, the area of CTAB head groups and the length of cetyl chains gradually decrease on average when solubilizing more cosurfactants. Cetyl chain compression is strong in the case of cosurfactants with n=4, whereas it is slightly compensated by an extension below the micellar surface in the case of longer cosurfactants. These conformational changes are related respectively to the formation of smaller spherical micelles and of anisotropic or swollen micelles.