Separation used for purification of recombinant proteins

The purification of molecules from recombinant cells may be strongly influenced by the molecular biology of gene isolation and expression. At the beginning of the process there may be a demand for information on the minute amounts of proteins and thus for ever increasingly sensitive techniques. Purification of recombinant proteins can differ from conventional purifications in several ways, depending on the solubility of the protein, occurrence in inclusion bodies, creation of fusion proteins with tags that enable simpler purification. Sometimes a (re)naturation step is required to get a bioactive protein. On the other hand, the techniques used in separation are essentially the same as for purification from the natural source and environment.     

Pitch-synchronous wavelet representations of speech and musicsignals

A new wavelet representation is explored. The transform is based on a pitch-synchronous vector representation and it adapts to the oscillatory or aperiodic characteristics of signals. Pseudo-periodic signals are represented in terms of an asymptotically periodic trend and aperiodic fluctuations at several scales. The transform reverts to the ordinary wavelet transform over totally aperiodic signal segments. The pitch-synchronous wavelet transform is particularly suitable to the analysis, rate-reduction coding and synthesis of speech signals and it may serve as a preprocessing block in automatic speech recognition systems. Feature extraction such as separation of voice from noise in voiced consonants is easily performed by means of partial wavelet expansions. A stochastic model of aperiodic fluctuations is proposed     

Physical properties and processing of Silphium integrifolium seeds to obtain oil and enriched protein meal

Silphium integrifolium Michx. (Silflower) has been a promising subject for domestication as a perennial oilseed crop. This work was carried out to investigate the seed processing aspect of this effort. Thousand seed weight, densities, and dimension of the seeds were evaluated, seed milling to obtain enriched kernel fraction was conducted, and initial characterization of the seed protein was performed. There was wide variation in flat seed length (11.5–20.8 mm), width (4.6–11.8 mm), and thickness (0.9–1.6 mm). The thousand seed weight was 23.8 g but the tapped bulk density was only 189.6 g/L due to the presence of wing around the seed's periphery. The kernel accounted for 56.1% of the seed weight and contained 31.0% oil. A kernel-enriched fraction with 79.6% purity was obtained by roller-milling, sifting, and air classification. Linoleic (62.3%) and oleic (19.6%) acids were the major fatty acids in the oil. The defatted enriched kernel fraction contained 63.41% crude protein. Globulin, glutelin, albumin, and prolamin accounted for 55.6%, 19.3%, 16.4%, and 8.7% of the soluble proteins, respectively. At an extraction pH of 9, protein solubility was 62%. Maximum solubility (70%) was obtained at pH 10 while minimum solubility of 9% occurred between pH 4 and 5.5. Aside from the oil, the dehulling of silflower seeds also produced a high-protein defatted meal, which may be used as is or as a starting material for enriching the protein further into a protein isolate.     

Structural basis of Bcl-xL recognition by a BH3-mimetic α/β-peptide generated by sequence-based design

The crystal structure of a complex between the prosurvival protein Bcl-x(L) and an α/β-peptide 21-mer is described. The α/β-peptide contains six β-amino acid residues distributed periodically throughout the sequence and adopts an α-helix-like conformation that mimics the bioactive shape of the Puma BH3 domain. The α/β-peptide forms all of the noncovalent contacts that have previously been identified as necessary for recognition of the prosurvival protein by an authentic BH3 domain. Comparison of our α/β-peptide:Bcl-x(L) structure with structures of complexes between native BH3 domains and Bcl-2 family proteins reveals how subtle adjustments, including variations in helix radius and helix bowing, allow the α/β-peptide to engage Bcl-x(L) with high affinity. Geometric comparisons of the BH3-mimetic α/β-peptide with α/β-peptides in helix-bundle assemblies provide insight on the conformational plasticity of backbones that contain combinations of α- and β-amino acid residues. The BH3-mimetic α/β-peptide displays prosurvival protein-binding preferences distinct from those of Puma BH3 itself, even though these two oligomers have identical side-chain sequences. Our results suggest origins for this backbone-dependent change in selectivity.     

Physical Properties and Fatty Acid Profiles of Oils from Black,Kidney, Great Northern,and Pinto Beans

Four common beans (black, kidney, great northern, and pinto) were extracted with hexane and found to contain about 2% triacylglycerols. The fatty acids in these bean oils were mainly linolenic (41.7–46 wt%), linoleic (24.1–33.4 wt%), palmitic (10.7–12.7 wt%) and oleic (5.2–9.5 wt%). Because of the high levels of polyunsaturated fatty acids, the bean oils had iodine values between 174 and 177 g/100 g (compared to 130 g/100 g for soybean oil). Yet, the bean oils exhibited high oxidative stability due to the presence of high amounts of tocopherols (2,670–2,970 ppm). The bean oils had lower pour points (−18 to −11 °C) compared to −9 °C for soybean oil. Among the four bean oils, kidney bean oil had the highest acid value (15.4 mg KOH/g) and kinematic viscosities over a wide range of temperatures.     

Post-treatment with high-power lasers to improve bond strength of adhesive systems to bleached dentin

To assess the effect of Er:YAG and diode lasers on the shear bond strength (SBS) of adhesive systems to bovine dentin submitted to bleaching with a high concentration agent. One hundred and twenty bovine dentin fragments were used. Fragments were distributed into 12 groups (n = 10) considering the bleaching (present or not), surface post-treatment (untreated, Er:YAG laser or diode laser) and adhesive system (total-etching or self-etching). Specimens received two applications of 38% hydrogen peroxide. Er:YAG laser (2940 nm, 200 mJ, 4 Hz) and diode laser (980 nm, 1.5 W) were applied for 15 s on bleached dentin surface. Restoration was performed with resin using split matrix. Specimens were submitted to SBS test and data (MPa) were analyzed by ANOVA and Tukey’s test (α = 0.05). SBS of bleached specimens decreased in comparison with non-bleached (p < 0.05). The highest values were obtained for the post-treatment with Er:YAG laser (p < 0.05). Total-etching adhesive was superior to self-etching system (p < 0.05). The irradiation of bleached dentin with Er:YAG laser followed by the application of the total-etching adhesive had similar SBS to unbleached dentin with no post-treatment (control) (p > 0.05). Er:YAG laser post-treatment followed by the total-etching adhesive system improve the bond strength of restorative material to bleached dentin.     

Control design for an autonomous wind based hydrogen production system

This paper presents a complete control scheme to efficiently manage the operation of an autonomous wind based hydrogen production system. This system comprises a wind energy generation module based on a multipolar permanent magnet synchronous generator, a lead-acid battery bank as short term energy storage and an alkaline von Hoerner electrolyzer. The control is developed in two hierarchical levels. The higher control level or supervisor control determines the general operation strategy for the whole system according to the wind conditions and the state of charge of the battery bank. On the other hand, the lower control level includes the individual controllers that regulate the respective module operation assuming the set-points determined by the supervisor control. These last controllers are approached using second-order super-twisting sliding mode techniques. The performance of the closed-loop system is assessed through representative computer simulations.     

The use of inductively coupled plasma mass spectrometry (ICP-MS) for the determination of toxic and essential elements in different types of food samples

This paper describes a simple method for the determination of sixteen elements in food samples by using inductively coupled plasma spectrometry (ICP-MS). Prior to analysis, 100–250 mg of powdered food samples were accurately weighed into a Teflon digestion vessel. Then, 4 ml of 20% v/v concentrated nitric acid and 2 ml of hydrogen peroxide were added. Decomposition of samples was carried out in a microwave digestion system. In order to verify the accuracy and precision of the proposed method, five Standard Reference Materials from the National Institute of Standards and Technology (NIST) (Whole Egg Powder RM 8415, Rice Flour SRM 1568a, Typical Diet SRM 1548a, Wheat Flour SRM 1567a and Bovine Muscle Powder RM 8414) were analyzed. Additional validation data are provided based on the analysis of 18 different types of food samples by the proposed method and using comparative methods with AAS as the detector.