Transfection of Mammalian Cells Using Block Copolypeptide Vesicles

An arginine‐leucine block copolypeptide (R₆₀L₂₀) is synthesized, which is capable of forming vesicles with controllable sizes, able to transport hydrophilic cargo across the cell membrane, and exhibit relatively low cytotoxicity. The R₆₀L₂₀ vesicles also possess the ability to deliver DNA into mammalian cells for transfection. Although the transfection efficiency is lower than that of the commercially available transfection agent Lipofectamine 2000, the R₆₀L₂₀ vesicles are able to achieve transfection with significantly lower cytotoxicity and immunogenicity. This behavior is potentially due to its stronger interaction with DNA which subsequently provides better protection against anionic heparin.

     

A new TVD flux-limiter method for solving nonlinear hyperbolic equations

We develop a new flux-limiter method based on the Richtmyer two-step Lax-Wendroff (R2LW) method coupled with a conservative upwind method and a nonconventional flux-limiter function. The proposed method is TVD stable and preserves the linear stability condition of the R2LW method. The numerical results show that this method improves on the approximations obtained by standard first-order and second-order TVD schemes. The new method provides accurate results for nonlinear hyperbolic equations with discontinuous solutions.     

Self-assembly and binding properties of a metallomacrocycle having two interactive binding subcavities

A metallomacrocycle containing two topologically discrete binding subcavities is self-assembled and shows a positive homotropic cooperative binding behavior.     

Laboratory Practices with the Wilson Plot Method

The Wilson plot method is a well-known tool used in practical applications and research activities that involve the analysis of different heat exchanger devices. Therefore, it is of interest to researchers and engineers working on heat transfer and related fields. Moreover, the application of this method is simple enough to be taught in laboratory practices with students. Taking into account the reasons cited above, a simple experimental apparatus has been designed and built at our laboratory. In this article, the calculation procedure to apply the Wilson plot method is explained and characteristic experimental results for a smooth tube and a spirally corrugated tube are reported. Moreover, the experimental results are compared with different correlations proposed in the literature.     

Fine Tuning of Vesicle Assembly and Properties Using Dual Hydrophilic Triblock Copolypeptides

The design, synthesis, and self‐assembly of the first dual hydrophilic triblock copolypeptide vesicles, ${\rm R}_{m}^{{\rm H}} {\rm E}_{n} {\rm L}_{o} $ and ${\rm K}_{m}^{{\rm P}} {\rm R}_{n}^{{\rm H}} {\rm L}_{o} $ , is reported. Variation of the two distinct hydrophilic domains is used to tune cellular interactions without disrupting the self‐assembled structure. The aqueous self‐assemblies of these triblock copolypeptides in water are characterized using microscopy and DLS. Cell culture studies are used to evaluate cytotoxicity as well as intracellular uptake of the vesicles. The ability of polypeptides to incorporate ordered chain conformations that direct self‐assembly, combined with the facile preparation of functional, multiblock copolypeptide sequences of defined lengths, allow the design of vesicles attractive for development as drug carriers.

     

The Immersed Interface Method for Simulating Two-Fluid Flows

We develop the immersed interface method (IIM) to simulate a two-fluid flow of two immiscible fluids with different density and viscosity. Due to the surface tension and the discontinuous fluid properties, the two-fluid flow has nonsmooth velocity and discontinuous pressure across the moving sharp interface separating the two fluids. The IIM computes the flow on a fixed Cartesian grid by incorporating into numerical schemes the necessary jump conditions induced by the interface. We present how to compute these necessary jump conditions from the analytical principal jump conditions derived in [Xu, DCDS, Supplement 2009, pp. 838-845]. We test our method on some canonical two-fluid flows. The results demonstrate that the method can handle large density and viscosity ratios, is second-order accurate in the infinity norm, and conserves mass inside a closed interface.     

Synthesis and Solid‐State,Solution, and Luminescence Properties of Near‐Infrared‐Emitting Neodymium(3+) Complexes Formed with Ligands Derived from Salophen

A series of free ligands, H₂ L ¹ , H₂ L ² , H₂ L ³ , and H₂ L ⁴ , designed for the coordination and sensitization of near‐infrared(NIR)‐emitting Nd³⁺ were synthesized by modifying the salophen Schiff base with different numbers and locations of Br‐substituents. The nature of the Nd³⁺ complexes in solution was determined to be [ML₂]^? by spectrophotometric titrations as an indication that the different substituents do not affect significantly the nature of the formed species. The structures were determined in the solid phase from X‐ray diffraction experiments. The stoichiometries and structures in the solid state are different from those observed in solution. We established that the structures in the solid state can be partially controlled by the crystallization conditions. The ligands L ¹ – L ⁴ have the ability to sensitize Nd³⁺ through intramolecular energy transfer from the ligand to the metal ion. We quantified that the numbers and locations of Br‐substituents control the emitted luminescence intensity of the complex by the heavy‐atom effect.