Physical and chemical adsorption of Mucor javanicus lipase on SBA-15 mesoporous silica. Synthesis, structural characterization, and activity performance

In this work a sample of SBA-15 mesoporous silica was synthesized and characterized by TEM, XRD, and N2 adsorption. The sample had a high value of specific surface area (1007 m2 g(-1)) and total pore volume (2.1 cm3 g(-1)). The pore diameter was 67 angstroms, so it was large enough to accommodate protein molecules inside the channels. Immobilization by physical adsorption of a commercial lipase preparation from Mucor javanicus was performed at different pH values (pH 5-8). pH 6 gave the highest lipase loading and hydrolytic activity of the corresponding biocatalyst. Chemical modification of the SBA-15 via glutardialdehyde allowed also the enzyme immobilization through chemical adsorption. This preparation was active toward tributyrin hydrolysis. On the contrary, very low activity toward triolein hydrolysis was observed. The reduction of the size of the channels due the immobilization process has been suggested as a possible explanation.     

Modeling the stability and the motion of DNA nucleobases on the gold surface

We simulate the structure and dynamics of the four DNA bases on the most stable gold surface. The experimental adsorption energies are reproduced to about 1 kcal mol(-1), and the existence of anchor points in the molecules is evidenced. The simulations also show that the bases drift on the gold surface with a degree of mobility that is not inversely proportional to the experimental (and calculated) desorption energies. When the same type of calculations is applied to pairs of bases it is seen that for at least two of them, namely GG and TT, there is a cooperative effect that increases their adsorption energy with respect to those of the single molecules. The molecular mobility on the surface is still present when a pair of interacting bases is considered.     

Priifer domains with class group generated by the classes of the invertible maximal ideals

In [2] and [3] we described the double coset decomposition for the modular group SL_r+s (Z) with respect to the congruence subgroup Р _r,s (m) for any positive integer m. In the present paper we obtain the double coset decomposition of SL_r+s (R) with respect to Р _r,s (I). Where R is a commutative ring with unioty 1, and I is a nonzero ideal in R such that R/I is the direct sum of local principal ideal rings; thus generalize the results obtained in [2] and [3].     

States of water,surface and rheological characterisation of a new biohydrogel as articular cartilage substitute

PVA based hydrogel was synthesised using, as crosslinking agent, trisodium trimetaphosphate (STMP) and its morphology was modified inducing a microporous structure to obtain potential substitutes for cartilage tissue. The hydrogel was characterised by Infrared Spectroscopy combined with Time of flight mass spectrometry (ToF‐SIMS) that confirmed the successful occurrence of crosslinking reaction, the hyphotised crosslinking arm and its homogeneous distribution. The mechanical spectra of the fully hydrated samples confirmed covalently crosslinked systems with a rheological behaviour similar to that of tibial cartilage. Further analysis in terms of water content measurements, thermal stability and cytotoxicity confirmed the applicability of such a hydrogel as cartilage substitute. Copyright © 2013 John Wiley & Sons, Ltd.     

New 9,10‐Secosteroids from Biotransformations of Bile Acids with Rhodococcus ruber

The biotransformations of cholic, deoxycholic, and hyocholic acids with Rhodococcus ruber are reported. In all biotransformations, the C₁₇‐side chain is partially degraded, and the new 9,10‐secosteroids 4a (54%) and 4b (55%) are obtained from cholic and deoxycholic acids, respectively. The loss of H₂O from C(11)? C(12) of secosteroids 4a and 4b affords the compounds 5a (5%) and 5b (20%), respectively. On the other hand, in the biotransformation of hyocholic acid with R. ruber the 9,10‐secosteroid 4c is not detected, but, rearranging to an intramolecular hemiacetal form, it evolves to the final furan derivative 6c (35%) by easy elimination of two molecules of H₂O. The new secosteroids were characterized by IR, NMR, and 2D‐NMR spectroscopy, and mass spectroscopy.     

Carbon Dots from Citric Acid and its Intermediates Formed by Thermal Decomposition

Thermal decomposition of citric acid is one of the most common synthesis methods for fluorescent carbon dots; the reaction pathway is, however, quite complex and the details are still far from being understood. For instance, several intermediates form during the process and they also give rise to fluorescent species. In the present work, the formation of fluorescent C-dots from citric acid has been studied as a function of reaction time by coupling infrared analysis, X-ray photoelectron spectroscopy, liquid chromatography/mass spectroscopy (LC/MS) with the change of the optical properties, absorption and emission. The reaction intermediates, which have been identified at different stages, produce two main emissive species, in the green and blue, as also indicated by the decay time analysis. C-dots formed from the intermediates have also been synthesised by thermal decomposition, which gave an emission maximum around 450 nm. The citric acid C-dots in water show short temporal stability, but their functionalisation with 3-aminopropyltriethoxysilane reduces the quenching. The understanding of the citric acid thermal decomposition reaction is expected to improve the control and reproducibility of C-dots synthesis.     

Trastuzumab quantification in serum: a new,rapid, robust ELISA assay based on a mimetic peptide that specifically recognizes trastuzumab

Trastuzumab, a humanized monoclonal antibody directed against the epidermal growth factor receptor 2 (HER2), is a milestone in the treatment of HER2-overexpressing breast cancer patients. An enzyme-linked immunosorbent assay (ELISA) for trastuzumab has been developed for routine use in the laboratory to support clinical and pharmacokinetic studies to optimize therapy. The method relies on an antigen peptide linked to a 96-well plate via the streptavidin/biotin system. The peptide sequence mimics the extracellular portion of the HER2 receptor that is recognized by trastuzumab. The calibration range of the assay is 10 to 360 ng/mL per well, corresponding to a trastuzumab serum concentration from 5 to 180 μg/mL with a lower limit of quantification of 10 μg/mL. Validation results demonstrate that trastuzumab can be accurately and precisely quantified in human serum using this assay. The procedure was also tested in sera obtained from breast cancer patients to evaluate trastuzumab serum levels, confirming the applicability of method that could be a valid assay to use in daily laboratory practice.     

SBA splitting for approximation of invariants in time-dependent Hamiltonian systems

Most physical phenomena are described by time-dependent Hamiltonian systems with qualitative features that should be preserved by numerical integrators used for approximating their dynamics. The initial energy of the system together with the energy added or subtracted by the outside forces, represent a conserved quantity of the motion. For a class of time-dependent Hamiltonian systems [8] this invariant can be defined by means of an auxiliary function whose dynamics has to be integrated simultaneously with the system’s equations. We propose splitting procedures featured by a SB³A property that allows to construct composition methods with a reduced number of determining order equations and to provide the same high accuracy for both the dynamics and the preservation of the invariant quantity.