Search

Most of cell penetrating peptides (CPPs) are rich in positively‐charged amino acids but the cationic property may provoke possible problems in practical applications. In this study, we carefully substituted the hydrophobic amino acids in the SAP(E) sequence, a rare example of negatively‐charged proline‐rich CPP, with cysteine for enhancement of cell penetrating activity as well as reversible conjugation of cargo molecules. Most substituents showed almost negligible cell penetrating activity, but a cysteine substituent on the 7th valine (SAP(E)‐7C) showed more improved cell penetrating activity than SAP(E). When treated to cells, the negatively‐charged SAP(E)‐7C exhibited much lower degree of co‐localization with acidic endosomes or lysosomes compared to positively‐charged TAT. SAP(E)‐7C could significantly enhance the PTX efficacy on MDA‐MB‐231 cells by non‐covalent complexation with PTX. As a proof‐of‐concept for covalent conjugation of cargo drugs, mercaptoethanol, a model drug, was conjugated to the cysteine residue of SAP(E)‐7C via a disulfide bond, and the glutathione‐dependent release from the conjugate was confirmed. The negatively‐charged SAP(E)‐7C with a cysteine handle can be a useful molecular module for the development of CPP‐based drug delivery carrier. [ABSTRACT FROM AUTHOR]

Magnetic resonance electrical impedance tomography (MREIT) attempts to provide conductivity images of an electrically conducting object with a high spatial resolution. When we inject current into the object, it produces internal distributions of current density J and magnetic flux density B = ([B.sub.x], [B.sub.y], [B.sub.z]). By using a magnetic resonance imaging (MRI) scanner, we can measure [B.sub.z] data where z is the direction of the main magnetic field of the scanner. Conductivity images are reconstructed based on the relation between the injection current and [B.sub.z] data. The harmonic [B.sub.z] algorithm was the first constructive MREIT imaging method and it has been quite successful in previous numerical and experimental studies. Its performance is, however, degraded when the imaging object contains low-conductivity regions such as bones and lungs. To overcome this difficulty, we carefully analyzed the structure of a current density distribution near such problematic regions and proposed a new technique, called the local harmonic [B.sub.z] algorithm. We first reconstruct conductivity values in local regions with a low conductivity contrast, separated from those problematic regions. Then, the method of characteristics is employed to find conductivity values in the problematic regions. One of the most interesting observations of the new algorithm is that it can provide a scaled conductivity image in a local region without knowing conductivity values outside the region. We present the performance of the new algorithm by using computer simulation methods. Index Terms--Conductivity image, domain decomposition, harmonic [B.sub.z], magnetic resonance electrical impedance tomography (MREIT).

The laser-induced fluorescence spectra (both fluorescence excitation and dispersed fluorescence) of jet-cooled 1,3-benzodioxan along with its ultraviolet absorption spectra have been recorded and analyzed in order to determine the vibrational quantum levels in both the ground and S1(π,π*) electronic excited states. A detailed energy map of the vibrational levels involving the six lowest frequency vibrations was established and utilized to better understand the structural and conformational differences between the ground and excited electronic states. The energies of more than a dozen vibrational excited states involving the out-of-plane ring twisting (ν47) and the out-of-plane ring bending (ν48) modes were determined for both S0 and S1 electronic states. Ab initio and density functional theory (DFT) calculations were also carried out to complement the experimental work. The data allowed one-dimensional potential energy functions in terms of the ring-twisting coordinate to be calculated. These show the molecule to have a twisting angle of 33° and a barrier to planarity of 4300±500 cm-1 for the S0 ground state and an angle of 24° and a barrier of 1500±200 cm-1 for the S1(π,π*) excited state. [ABSTRACT FROM AUTHOR]

Dual-energy CT can be represented as the dual-energy equations by decomposing the linear attenuation coefficient of the X-ray scanned object into two material basis functions of photoelectric absorption and Compton scatter. To solve the dual-energy equations, in this paper, we apply the mean-value theorem for integrals and propose a new projection-based iterative algorithm. We discuss the convergence of the proposed algorithm and carry out various numerical simulations for demonstrating its feasibility. [ABSTRACT FROM PUBLISHER]