Polyclonal Antibodies in Microplates to Predict the Maximum Adsorption Activities of Enzyme/Mutants from Cell Lysates

With microplate-immobilized polyclonal antibodies against a starting enzyme or its active mutant bearing consistent accessible epitopes, the maximum activity of an adsorbed enzyme/mutant (Vs) was predicted for comparison to recognize weakly-positive mutants. Rabbit antisera against Escherichia coli alkaline phosphatase (ECAP) were fractionated with 33% ammonium sulfate to yield crude polyclonal antibodies for conventional immobilization in 96-well microplates. The response curve of the activities of ECAP/mutant adsorbed by the immobilized polyclonal antibodies to protein quantities from a cell lysate was fit to an approximation model to predict Vs. With 0.4 μg crude polyclonal antibody for immobilization, Vs was consistent for ECAP in cell lysates bearing fourfold differences in its apparent specific activities when its abundance was greater than 0.9%. The ratio of Vs of the mutant R168K to that of ECAP was 1.5?±?0.1 (n?=?2), consistent with that of their specific activities after affinity purification. Unfortunately, the prediction of Vs with polyclonal antibodies that saturated microplate wells was ineffective to Pseudomonas aeruginosa arylsulfatase bearing less than 2% specific activity of ECAP. Therefore, with microplate-immobilized polyclonal antibodies to adsorb enzyme/mutants from cell lysates, high-throughput prediction of Vs was practical to recognize weakly-positive mutants of starting enzymes bearing fairly-high activities.     

Emerging 3D‐Printed Electrochemical Energy Storage Devices: A Critical Review

Three‐dimensional (3D) printing, a layer‐by‐layer deposition technology, has a revolutionary role in a broad range of applications. As an emerging advanced fabrication technology, it has drawn growing interest in the field of electrochemical energy storage because of its inherent advantages including the freeform construction and controllable 3D structural prototyping. This article focuses on the topic of 3D‐printed electrochemical energy storage devices (EESDs), which bridge advanced electrochemical energy storage and future additive manufacturing. Basic 3D printing systems and material considerations are described to provide a fundamental understanding of printing technologies for the fabrication of EESDs. The performance metrics of 3D‐printed EESDs are then given and the related performance optimization strategies are discussed. Next, the recent advances of 3D‐printed EESDs, including sandwich‐type and in‐plane architectures, are summarized. Conclusions and future perspectives with some unique challenges and important directions are then discussed. It can be expected that, with the help of 3D printing technology, the development of advanced electrochemical energy storage systems will be greatly promoted.     

Metabolic engineering of Escherichia coli for biosynthesis of hyaluronic acid

Engineering of hyaluronic acid (HA) biosynthetic pathway in recombinant Escherichia coli as production host is reported in this work. A hyaluronic acid synthase (HAS) gene, sphasA, from Sreptococcus pyogenes with the start codon gtg to atg mutant, was expressed in recombinant E. coli with or without the genes ugd, galF and glmU, which are analogs of hasB, hasC and hasD from Streptococcus, respectively, encoding UDP-glucose 6-dehygrogenase, Glucose-1-P uridyltransferase, and N-acetyl glucosamine uridyltransferase enzymes in the HA biosynthetic pathway. The single, double and triple organized artificial operons of sphasA, ugd, galF and glmU were designed and constructed using the inducible plasmid backbone of pMBAD. Only the triple expression recombinant, Top10/pMBAD-spABC, generated a relatively high titer of HA (approximately 48 mg/l at 48 h), indicating that both of the enzymes encoded by ugd and galF are essential for HA biosynthesis. A new gene of ssehasA with identical protein sequence of seHAS from Streptococcus equisimilis, was artificially synthesized after substituting all of the rare codons in the natural sehasA. The HA titer at 24 h flask culture increased to approximately 190 mg/l in sseAB and 160 mg/l in sseABC, respectively. Sorbitol could be used as another carbon source for HA accumulation, and the metabolic pathway for HA synthesis in a recombinant E. coli was presented. The concentration of Mg(2+) cofactor of HA synthase was optimized and a cell growth inhibition phenomenon was observed during HA accumulation. Molecular weight (MW) measurements revealed that the mean MW of HA produced from the recombinant E. coli under different conditions ranges from approximately 3.5x10(5) to 1.9x10(6)Da, indicating that the recombinant E. coli can be used as a potential host candidate for industrial production of HA.     

Comparative evaluation of different cell disruption methods for the release of recombinant hepatitis B core antigen from <Emphasis Type="Italic">Escherichia coli</Emphasis>

A comparative evaluation of five different cell-disruption methods for the release of recombinant hepatitis B core antigen (HBcAg) from Escherichia coli was investigated. The cell disruption techniques evaluated in this study were high-pressure homogenization, batch-mode bead milling, continuous-recycling bead milling, ultrasonication, and enzymatic lysis. Continuous-recycling bead milling was found to be the most effective method in terms of operating cost and time. However, the highest degree of cell disruption and amounts of HBcAg were obtained from the high-pressure homogenization process. The direct purification of HBcAg from the unclarified cell disruptate derived from high-pressure homogenization and bead milling techniques, using batch anion-exchange adsorption methods, showed that the conditions of cell disruption have a substantial effect on subsequent protein recovery steps.     

Neuraminidase 1 is a negative regulator of lysosomal exocytosis

Lysosomal exocytosis is a Ca2+-regulated mechanism that involves proteins responsible for cytoskeletal attachment and fusion of lysosomes with the plasma membrane. However, whether luminal lysosomal enzymes contribute to this process remains unknown. Here we show that neuraminidase NEU1 negatively regulates lysosomal exocytosis in hematopoietic cells by processing the sialic acids on the lysosomal membrane protein LAMP-1. In macrophages from NEU1-deficient mice, a model of the disease sialidosis, and in patients' fibroblasts, oversialylated LAMP-1 enhances lysosomal exocytosis. Silencing of LAMP-1 reverts this phenotype by interfering with the docking of lysosomes at the plasma membrane. In neu1-/- mice the excessive exocytosis of serine proteases in the bone niche leads to inactivation of extracellular serpins, premature degradation of VCAM-1, and loss of bone marrow retention. Our findings uncover an unexpected mechanism influencing lysosomal exocytosis and argue that exacerbations of this process form the basis for certain genetic diseases.     

Inducible and selective erasure of memories in the mouse brain via chemical-genetic manipulation

Rapid and selective erasures of certain types of memories in the brain would be desirable under certain clinical circumstances. By employing an inducible and reversible chemical-genetic technique, we find that transient alphaCaMKII overexpression at the time of recall impairs the retrieval of both newly formed one-hour object recognition memory and fear memories, as well as 1-month-old fear memories. Systematic analyses suggest that excessive alphaCaMKII activity-induced recall deficits are not caused by disrupting the retrieval access to the stored information but are, rather, due to the active erasure of the stored memories. Further experiments show that the recall-induced erasure of fear memories is highly restricted to the memory being retrieved while leaving other memories intact. Therefore, our study reveals a molecular genetic paradigm through which a given memory, such as new or old fear memory, can be rapidly and specifically erased in a controlled and inducible manner in the brain.     

Identification and characterization of an archaeon-specific riboflavin kinase

The riboflavin kinase in Methanocaldococcus jannaschii has been identified as the product of the MJ0056 gene. Recombinant expression of the MJ0056 gene in Escherichia coli led to a large increase in the amount of flavin mononucleotide (FMN) in the E. coli cell extract. The unexpected features of the purified recombinant enzyme were its use of CTP as the phosphoryl donor and the absence of a requirement for added metal ion to catalyze the formation of FMN. Identification of this riboflavin kinase fills another gap in the archaeal flavin biosynthetic pathway. Some divalent metals were found to be potent inhibitors of the reaction. The enzyme represents a unique CTP-dependent family of kinases.