Yen-Chih Chen

A novel DNA selection and direct extraction process and its application in DNA recombination.

In the conventional bench‐top approach, the DNA recombination process is time‐ and effort‐consuming due to laborious procedures lasting from several hours to a day. A novel DNA selection and direct extraction process has been proposed, integrated and tested on chip. The integrative microfluidic chip can perform the whole procedure of DNA recombination, including DNA digestion, gel electrophoresis, DNA extraction and insert‐vector ligation within 1 h. In this high‐throughput design, the manual gel cutting was replaced by an automatic processing system that performed high‐quality and high‐recovery efficiency in DNA extraction process. With no need of gel‐dissolving reagents and manipulation, the application of selection and direct extraction process could significantly eliminate the risks from UV and EtBr and also facilitate DNA recombination. Reliable output with high success rate of cloning has been achieved with a significant reduction in operational hazards, required materials, efforts and time.

Neuronal aging: learning from C. elegans.

The heterogeneity and multigenetic nature of nervous system aging make modeling of it a formidable task in mammalian species. The powerful genetics, simple anatomy and short life span of the nematode Caenorhabditis elegans offer unique advantages in unraveling the molecular genetic network that regulates the integrity of neuronal structures and functions during aging. In this review, we first summarize recent breakthroughs in the morphological and functional characterization of C. elegans neuronal aging. Age-associated morphological changes include age-dependent neurite branching, axon beading or swelling, axon defasciculation, progressive distortion of the neuronal soma, and early decline in presynaptic release function. We then discuss genetic pathways that modulate the speed of neuronal aging concordant with alteration in life span, such as insulin signaling, as well as cell-autonomous factors that promote neuronal integrity during senescence, including membrane activity and JNK/MAPK signaling. As a robust genetic model for aging, insights from C. elegans neuronal aging studies will contribute to our mechanistic understanding of human brain aging.

Genetic analysis of a novel tubulin mutation that redirects synaptic vesicle targeting and causes neurite degeneration in C. elegans.

Neuronal cargos are differentially targeted to either axons or dendrites, and this polarized cargo targeting critically depends on the interaction between microtubules and molecular motors. From a forward mutagenesis screen, we identified a gain-of-function mutation in the C. elegans α-tubulin gene mec-12 that triggered synaptic vesicle mistargeting, neurite swelling and neurodegeneration in the touch receptor neurons. This missense mutation replaced an absolutely conserved glycine in the H12 helix with glutamic acid, resulting in increased negative charges at the C-terminus of α-tubulin. Synaptic vesicle mistargeting in the mutant neurons was suppressed by reducing dynein function, suggesting that aberrantly high dynein activity mistargeted synaptic vesicles. We demonstrated that dynein showed preference towards binding mutant microtubules over wild-type in microtubule sedimentation assay. By contrast, neurite swelling and neurodegeneration were independent of dynein and could be ameliorated by genetic paralysis of the animal. This suggests that mutant microtubules render the neurons susceptible to recurrent mechanical stress induced by muscle activity, which is consistent with the observation that microtubule network was disorganized under electron microscopy. Our work provides insights into how microtubule-dynein interaction instructs synaptic vesicle targeting and the importance of microtubule in the maintenance of neuronal structures against constant mechanical stress.

Reliability of Ultrasonography in Evaluating Hyoid Bone Movement

Background Timely and adequate laryngeal elevation along with hyoid bone movement is an essential component of the swallowing movement under normal physiological conditions. The purpose of this study was to verify the reproducibility of using ultrasonography to evaluate hyoid bone displacement during swallowing through the assessment of inter- and intrarater reliability and examine its accuracy by comparing the results with videofluoroscopic swallowing study (VFSS). Methods A self-designed water balloon was fixed to the transducer, which provided good contact between the transducer and the submental skin. Ten participants with dysphagia were recruited. The measurements of hyoid bone displacement using ultrasonography were performed by two of the authors. All the participants underwent ultrasonographic examinations and VFSS within 24 hours. Results The intrarater intraclass correlation coefficient (ICC) of the two examiners was 0.996 and 0.959, respectively (p < 0.01); the interrater ICC between the two examiners was 0.892 (p < 0.05). ICCs between VFSS and ultrasonography for two researchers were 0.815 and 0.916 (p < 0.01). Conclusion Submental ultrasonography is a reliable and accurate method for assessing the hyoid bone movement.

An ultra-broadband low noise amplifier in GaAs 0.1-μm pHEMT process for radio astronomy application

An ultra-wideband low noise amplifier (LNA) in 0.1-μm GaAs pHEMT process designed with the inductive feedback gain-boosting technique is presented. The proposed LNA is designed with the feedback structure to compensate the high frequency gain and improve the gain flatness. With only two stages, the 3-dB bandwidth of the LNA covers from 3.8 to 19.8 GHz and 1-dB bandwidth covers from 4.2 to 17.3 GHz. The measured small signal gain (S21) is 20.4 dB and the measured noise figure is 1.2 dB at 14 GHz with dc power consumption of 40 mW. The chip area is 1.5 × 1.0 mm2.

A 4.6-GHz Class-F −1 high power CMOS power amplifier

A 4.6-GHz Class-F−1 CMOS power amplifier implemented in 0.18-μm CMOS process for wireless applications with high output power and high efficiency is proposed. By using harmonics tuning technique and cascode devices, the proposed power amplifier achieves an output power of 27.8-dBm with power-add-efficiency (PAE) of 32% and quiescent 158-mW dc power consumption.

GEMPLS: a new QSAR method combining generic evolutionary method and partial least squares

We have proposed a new method for quantitative structure-activity relationship (QSAR) analysis. This tool, termed GEMPLS, combines a genetic evolutionary method with partial least squares (PLS). We designed a new genetic operator and used Mahalanobis distance to improve predicted accuracy and speed up a solution for QSAR. The number of latent variables (lv) was encoded into the chromosome of GA, instead of scanning the best lv for PLS. We applied GEMPLS on a comparative binding energy (COMBINE) analysis system of 48 inhibitors of the HIV-1 protease. Using GEMPLS, the cross-validated correlation coefficient (q2) is 0.9053 and external SDEP (SDEPex) is 0.61. The results indicate that GEMPLS is very comparative to GAPLS and GEMPLS is faster than GAPLS for this data set. GEMPLS yielded the QSAR models, in which selected residues are consistent with some experimental evidences.

Comparative Molecular Binding Energy Analysis of HIV-1 Protease Inhibitors Using Genetic Algorithm-Based Partial Least Squares Method

Comparative molecular binding energy analysis (COMBINE) [1] is a helpful approach for estimation of binding affinity of congeneric ligands that bind to a common receptor. The essence of COMBINE is that the ligand-receptor interaction energies are decomposed into residue-based energy contributions, and then the partial least squares (PLS) analysis is applied to correlate energy features with biological activity. However, the predictive performance of PLS model drops with the increase of number of noisy variables. With regard to this problem genetic algorithm (GA) combined with PLS approach (GAPLS) [2] for feature selection has demonstrated the improvement on the prediction and interpretation of model. Therefore, the purpose of this paper is to derive a more accurate and more efficient GAPLS in COMBINE by introducing a number of successive refinements.