Designing Molecular Printboards: A Photolithographic Platform for Recodable Surfaces

A light induced strategy for the design of β‐cyclodextrin (CD) based supramolecular devices is introduced, presenting a novel tool to fabricate multifunctional biointerfaces. Precision photolithography of a modified β‐CD was established on a light sensitive tetrazole surface immobilized on a bioinspired polydopamine (PDA) anchor layer via various shadow masks, as well as via direct laser writing (DLW), in order to craft any desired printboard design. Interfacial molecular recognition provided by light generated cavitate domains was demonstrated via spatially resolved encoding, erasing, and recoding of distinct supramolecular guest patterns. Thus, the light directed shaping of receptor monolayers introduces a powerful path to control supramolecular assemblies on various surfaces.     

A Safety Strategy for Producing Poly(Acrylic Acid) of Low Molar Mass

The synthesis of poly(acrylic acid) (PAA) of low molar mass under safe conditions is difficult due to the high polymerization rate of acrylic acid (AA) and the fast heat generation. The aqueous‐solution “semibatch” polymerization of non‐ionized AA in almost starved conditions involves high initiator loads when low molar masses are required. This article proposes the simultaneous feeding of AA and nonconventional chain transfer agents (CTA) as a strategy aimed at controlling both the molar masses and the generated heat rate. Three CTAs are investigated: 2‐mercaptoethanol, thioglycolic acid, and isopropyl alcohol. Even when PAA of relatively low molar mass can be produced by adequately selecting the flow rates and concentrations of both AA and CTA, it is found that the nature of CTA can have a significant effect on the polymerizations kinetics. The mechanisms responsible for these effects are discussed with the help of a representative mathematical model.

     

Protein unfolding studied by fluorescence methods and electrical impedance spectroscopy: the cases of Cratylia mollis and Concanavalin A

This work is dedicated to the investigation of the prevailing molecular interactions between Cratylia mollis (Cramoll) and Concanavalin A (Con A) lectins and ionic (sodium dodecylsulfate, SDS) and non-ionic (Triton X-100, TX-100) surfactants, where we have used electrical impedance spectroscopy to map the dielectric characteristics of mixed lectin/surfactant solutions. The disorder induced in the lectin conformation is proportional to the extent of the access of the surfactant to the fluorophore present in the protein, resulting in its progressive unfolding. The complete unfolding of the lectin is associated to the formation of micelles in the core of the protein, each one of them containing a large number of detergent molecules, and therefore the process can be accompanied by measuring the electrical response of the binary surfactant/lectin system. For instance, the change in the real part of the impedance as a function of the relative concentration of the surfactant in the binary solution exhibits a breaking in its linear behavior that can be taken as indicative of a qualitative change in the environment surrounding the protein residue. We consider these results strong evidence in favor of using impedance spectroscopy methods for the analysis of protein-surfactant associations and for the characterization of the interactions that must prevail when the protein unfolds as the relative surfactant concentration is increased in aqueous solutions of these binary systems.     

Full enzymatic hydrolysis of commercial sucrose laurate by immobilized-stabilized derivatives of lipase from Thermomyces lanuginosa

Sucrose laurate is a detergent that is useful for various biochemical applications because it is a green compound and is easily degradable after hydrolysis with a lipase or esterase. One problem observed in the process of sucrose laurate degradation is that most commercial detergent preparations are impure, necessitating the hydrolysis of all of the sucrose esters present in the preparation, all of them with detergent properties. In this article, a highly active catalyst, which is able to perform the hydrolysis of commercial sucrose laurate, is presented. The use of glyoxyl agarose preparations of a previously aminated Thermomyces lanuginosa lipase (TLL) enabled complete hydrolysis, in less than 30 min, of all of the compounds that comprise the mixture. In addition, this derivative is stable in the presence of 20% ethanol, which is necessary to prevent microbial contamination.     

Analysis of sulfated peptides from the skin secretion of the Pachymedusa dacnicolor frog using IMAC-Ga enrichment and high-resolution mass spectrometry

Immobilized metal ion affinity chromatography (IMAC) has been widely used for the enrichment of phosphopeptides, whereas no report exists describing the use of IMAC columns for the enrichment of sulfopeptides. In this study, we used IMAC-Ga microcolumns for the enrichment of sulfopeptides from a complex mixture of peptides, extracted from skin secretions of the Pachymedusa dacnicolor frog. The enriched fraction obtained by IMAC-Ga was analyzed by liquid chromatograpy/electrospray ionization mass spectrometry (LC/ESI-MS) in an Orbitrap XL and by matrix-assisted laser desorption/ionization time-of-flight time-of-flight (MALDI-TOF/TOF) in an ABI 4800 instrument. From this fraction, different sulfated and non-sulfated peptides belonging to the caerulin and bradykinin families were structurally characterized. Other interesting negatively charged groups, such as phosphate adducts of dermaseptins and pyridoxal phosphate attached to a protease inhibitor, were also characterized. Unexpectedly, some dermaseptin antimicrobial peptides were also enriched by IMAC-Ga and a Sauvatine-like peptide was also fully sequenced. Furthermore, neutral loss of sulfated peptides and their fragmentation patterns in the gas phase were also compared using collision-induced dissociation (CID) and high-energy collision dissociation (HCD). Our present study provides evidence that IMAC-Ga enrichment is a fast, useful and promising method for high-throughput analysis of sulfated-peptides, since high-resolution mass spectrometers can be used for this purpose.     

Fast determination of thyroid stimulating hormone in human blood serum without chemical preprocessing by using infrared spectroscopy and least squares support vector machines

The least squares support vector machines (LS-SVM) was used to model infrared spectral data for TSH hormone secreted by thyroid, which regulates the basal metabolic rate. This model was used for direct estimation of the content of TSH in blood serum samples, and the results were comparable with those obtained with the conventional analytical method based on chemoluminescence methodology. Excellent agreement was observed between the conventional method and the newly developed calibration model based in analysis of spectral data with LS-SVM. The latter has clear advantages, because it is fast and requires no reagent once the measurements were done directly in the serum by using a simple mid-infrared spectrometer in the ATR mode. An important advantage observed in this calibration method based on LS-SVM is the remarkable capacity to avoid overfitting in the model-building step, that is, the developed method is highly robust.     

Continuous photochemical generation of catalytically active [CpRu]+ complexes from CpRu(η6-C6H6)PF6

Inter- and intramolecular ene-yne coupling reactions catalyzed by a species generated in situ via photolysis of CpRu(η(6)-C(6)H(6))PF(6)--an inexpensive, readily available, and shelf-stable complex--have been demonstrated under conditions of continuous flow. Importantly, the catalyst can be recovered quantitatively at the end of the reaction. Various functional groups are tolerated by the reaction, which affords skipped diene products in high yields.     

Combination of cysteine- and oligomerization domain-mediated protein immobilization on a surface plasmon resonance (SPR) gold chip surface

Here we report an effective method for protein immobilization on a surface plasmon resonance (SPR) gold chip, describing the combination of cysteine- and oligomerization domain-mediated immobilization of enhanced green fluorescent protein (EGFP) as a model protein for the purpose of orientation-controlled surface density packing. In order to facilitate the oligomerization of EGFP, the dimeric and trimeric constructs derived from GCN4- leucine zipper domain were chosen for multimeric EGFP assembly. For orientation-controlled immobilization of the protein, EGFP modified with cysteine residues showing excellent orientation on a gold chip was used as a starting protein, as previously reported in our earlier study (Anal. Chem., 2007, 79, 2680-2687). Constructs of EGFP with oligomerization domains were genetically engineered, and corresponding fusion proteins were purified, applied to a gold chip, and then analyzed under SPR. The immobilized EGFP density on a gold chip increased according to the states of protein oligomerization, as dimeric and trimeric EGFPs displayed better adsorption capability than monomeric and dimeric forms, respectively. Fluorescence measurement corroborated the SPR results. Taken together, our findings indicated that the combination of cysteine- and oligomerization domain-mediated immobilization of protein could be used in SPR biosensor applications, allowing for an excellent orientation and high surface density simultaneously.     

Innovative synthetical and structural features of new aryltellurenyl iodides

The syntheses and the structural characterization of the compounds [(mes)₂Te–Te(I)mes], (PyH)[mesTeI₃(I₃)] (mes = mesityl = 2,4,6-trimethylphenyl; Py = pyridine), (PyH)₃[dmephTeI₂(I₂)]₂(I₃) (dmeph = 2,6-dimethylphenyl), (PyH)₂[RTeI₄]₂·(CH₃)CO(CH₃)·C₆H₅CH₃ (R = p-tert-butylphenyl) and (PyH)₂[PhTeI₄]₂ (Ph = phenyl) are presented. Some earlier analog preparations are compared and the influence of ortho substituents in the aryl group on the oxidation state of tellurium is discussed, as well as the observed conditions for the formation of poly-iodides chains.     

Structure-guided redesign of D-fructose-6-phosphate aldolase from E. coli: remarkable activity and selectivity towards acceptor substrates by two-point mutation

Structure-guided re-design of the acceptor binding site of D-fructose-6-phosphate aldolase from E. coli leads to the construction of FSA A129S/A165G double mutant with an activity between 5- to >900-fold higher than that of wild-type towards N-Cbz-aminoaldehyde derivatives.