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[en] Covalent binding of carcinogen to nucleic acids is believed to be an essential component of the carcinogenic process, so it is desirable to have highly sensitive and specific methods for detecting such adducts in cells and tissues exposed to known and suspected carcinogens. A radioimmunoassay is here described capable of detecting nanogram amounts of DNA adducts resulting from the covalent binding of the carcinogen N-2-acetylaminofluorene and its activated N-acetoxy derivative. (author)
[en] p53 is a tumor suppressor protein which is either lost or inactivated in a large majority of tumors. The small molecule 2-phenylethynesulfonamide (PES) was originally identified as the inhibitor of p53 effects on the mitochondrial death pathway. In this report we demonstrate that p53 protein from PES-treated cells was detected in reduced mobility bands between molecular weights 95–220 kDa. Resolution of p53 aggregates on urea gel was unable to reduce the high molecular weight p53 aggregates, which were shown to be primarily located in the nucleus. Therefore, our data suggest that PES exerts its effects through covalent cross-linking and nuclear retention of p53. - Highlights: • p53 protein is in high molecular weight complexes in the nucleus of PES-treated cells. • PES is a drug that inhibits pro-apoptotic p53 action at the mitochondria. • We propose that PES action involves cross-linking and nuclear retention of p53.
[en] The effective biofunctionalization of nanoparticles is crucial for biomedical applications. In this study we investigated the covalent biofunctionalization of magnetic nanoparticles based on carbodiimide activation. An important aspect in the covalent biofunctionalization of nanoparticles has been neglected, namely pre-concentration. Exploiting the electrostatic attraction forces between a protein and the nanoparticle surface will favor the covalent immobilization. We showed that low ionic strength buffers with a pH slightly lower than the pI of the selected biomolecules is needed to increase the yield of covalent immobilization. Additionally, it is demonstrated that the covalently immobilized proteins are bioactive, relying on a sandwich assay using gold nanoparticles as reporter labels.
[en] A porous organic-inorganic hybrid sol-gel carbon composite has been developed and used for surface covalent bonding of an enzyme for biosensing applications, illustrated by glucose oxidase (GOD). The composite comprises graphite powder, ferrocene, and an amino- and methyl-silicate backbone. The graphite powder provides the conductivity for the electrode and ferrocene acts as the mediator for signal transduction from the active center of the enzyme to the electron conductive surface. The presence of amine groups in the sol-gel silicate network allows for the covalent bonding sites for the enzyme via the carbodiimide reaction. The hydrophobicity and hydrophilicity properties of the electrode surface are controlled by the amine and methyl groups of the silicate network. Systematic optimization of the composite composition has been carried out and the performance of the glucose biosensor has been investigated. The optimal electrode gives a linear response range of 0.1-27 mM glucose with a sensitivity of 1.30 μA mM-1 and detection limit (S/N = 3) of 26 μM
[en] Using the carbon nanotube (CNT) as the 1D building block, various 2D covalent CNT networks are theoretically built. The specific heat of these CNT networks is calculated by the quantized molecular structural mechanics method. The effect of the geometric parameters of networks on their specific heat is found to be small at all temperature levels. At high temperatures this effect even vanishes. A general formula for the specific heat of these 2D CNT networks is given. This formula depends only on the building block of the networks. Besides, the specific heat per unit area of these CNT networks with different geometric properties are also explored and found to be extremely low. The predicted thermal properties of the CNT networks reveal their potential applications in fabricating excellent loudspeakers.
[en] Highlights: • Synthesis of XC-treated GNPs using simple and economical method was successful. • High stability of XC-treated GNPs nanofluids were recorded after 15 days. • XC-treated GNPs nanofluids shows good performance for thermophysical properties. • A potentially material to be used in thermal applications was introduced.
[en] The vast majority of the proteins in nature are under thermodynamic control, consistent with the universally accepted notion that proteins exist in their thermodynamically most stable state. Yet, recently a number of examples of proteins whose fold is under kinetic control have come to light. Their functions and environments vary. The first among these are some proteases, discovered in the early 1990s. There, an N-terminal proregion is self-cleaved after the protein folded, leaving the remainder of the chain in a kinetically trapped state. A related scenario was observed for microcin J25, an antibacterial peptide. This peptide presents a trapped covalently knotted conformation. The third and the most recently discovered case is the multidrug-resistant transporter protein, P-glycoprotein. There, a synonymous 'silent' mutation leads to ribosome stalling with a consequent altered kinetically trapped state. Here we argue that in all three examples, the N-terminal plays the role of an intra-molecular chaperone, that is, the N-terminal conformation selects among all competing local conformations of a downstream segment. By providing a pattern, the N-terminal chaperone segment assists the protein folding process. If the N-terminal is subsequently cleaved, the protein can be under kinetic control, since it is trapped in a thermodynamically less-stable state. (perspective)