Effects of Content Support and Planning Instruction on Discourse Connection in EFL Argumentative Writing.

Discourse connection is a challenging aspect of writing in a second language. This study seeks to investigate the effects of two classroom instructions on discourse connection in writing for EFL college students, focusing on their argumentative writing. Three classes were exposed to different pre-task conditions: receiving reading materials that provide content support for the writing, receiving planning instructions on effective outlining, and receiving no resources. The results showed that the instructions helped students attain better overall coherence in writing. However, noticeable differences between the two experimental groups emerged in terms of cohesion features. The reading group was found to employ more lexical cohesion devices in writing than the outline group, which indicated a heightened genre awareness. This inquiry helped us identify the reading group's alignment with content support materials, particularly the change in stance as a factor that contributes to a higher level of lexical cohesion in writing.

Pragmatic Competence and Willingness to Communicate Among L2 Learners of Chinese.

Research in second language (L2) pragmatics has paid increasing attention to learners' individual differences, but few studies have examined the relationship between learners' willingness to communicate (WTC) in L2 and their pragmatic competence. To this end, this study investigates the association between WTC and pragmatic awareness and comprehension of Chinese as a second language (CSL) learners. A total of 80 CSL learners studying abroad in three universities in China participated in this study. Data were collected through a WTC questionnaire, a self-perceived communication competence (SPCC) questionnaire, a pragmatic awareness judgment task, and a multiple-choice test for pragmatic comprehension. Statistical analyses were conducted to explore the relationship between the learners' pragmatic awareness and pragmatic comprehension on the one hand and their WTC and SPCC in L2 on the other. The findings indicated that SPCC correlated positively with the learners' L2 pragmatic comprehension, but not with their L2 pragmatic awareness. No correlation was found between WTC and pragmatic awareness and comprehension. The results suggest that SPCC may contribute to learners' L2 pragmatic comprehension; some implications for teaching and future research directions are also discussed.

Significant improvement of oxidase activity through the genetic incorporation of a redox-active unnatural amino acid.

While nature employs various covalent and non-covalent strategies to modulate tyrosine (Y) redox potential and pK a in order to optimize enzyme activities, such approaches have not been systematically applied for the design of functional metalloproteins. Through the genetic incorporation of 3-methoxytyrosine (OMeY) into myoglobin, we replicated important features of cytochrome c oxidase (CcO) in this small soluble protein, which exhibits selective O2 reduction activity while generating a small amount of reactive oxygen species (ROS). These results demonstrate that the electron donating ability of a tyrosine residue in the active site is important for CcO function. Moreover, we elucidated the structural basis for the genetic incorporation of OMeY into proteins by solving the X-ray structure of OMeY specific aminoacyl-tRNA synthetase complexed with OMeY.

Ultrafast photoinduced electron transfer in green fluorescent protein bearing a genetically encoded electron acceptor.

Electron transfer (ET) is widely used for driving the processes that underlie the chemistry of life. However, our abilities to probe electron transfer mechanisms in proteins and design redox enzymes are limited, due to the lack of methods to site-specifically insert electron acceptors into proteins in vivo. Here we describe the synthesis and genetic incorporation of 4-fluoro-3-nitrophenylalanine (FNO2Phe), which has similar reduction potentials to NAD(P)H and ferredoxin, the most important biological reductants. Through the genetic incorporation of FNO2Phe into green fluorescent protein (GFP) and femtosecond transient absorption measurement, we show that photoinduced electron transfer (PET) from the GFP chromophore to FNO2Phe occurs very fast (within 11 ps), which is comparable to that of the first electron transfer step in photosystem I, from P700* to A0. This genetically encoded, low-reduction potential unnatural amino acid (UAA) can significantly improve our ability to investigate electron transfer mechanisms in complex reductases and facilitate the design of miniature proteins that mimic their functions.

Defining the role of tyrosine and rational tuning of oxidase activity by genetic incorporation of unnatural tyrosine analogs.

While a conserved tyrosine (Tyr) is found in oxidases, the roles of phenol ring pKa and reduction potential in O2 reduction have not been defined despite many years of research on numerous oxidases and their models. These issues represent major challenges in our understanding of O2 reduction mechanism in bioenergetics. Through genetic incorporation of unnatural amino acid analogs of Tyr, with progressively decreasing pKa of the phenol ring and increasing reduction potential, in the active site of a functional model of oxidase in myoglobin, a linear dependence of both the O2 reduction activity and the fraction of H2O formation with the pKa of the phenol ring has been established. By using these unnatural amino acids as spectroscopic probe, we have provided conclusive evidence for the location of a Tyr radical generated during reaction with H2O2, by the distinctive hyperfine splitting patterns of the halogenated tyrosines and one of its deuterated derivatives incorporated at the 33 position of the protein. These results demonstrate for the first time that enhancing the proton donation ability of the Tyr enhances the oxidase activity, allowing the Tyr analogs to augment enzymatic activity beyond that of natural Tyr.

Significant expansion of fluorescent protein sensing ability through the genetic incorporation of superior photo-induced electron-transfer quenchers.

Photo-induced electron transfer (PET) is ubiquitous for photosynthesis and fluorescent sensor design. However, genetically coded PET sensors are underdeveloped, due to the lack of methods to site-specifically install PET probes on proteins. Here we describe a family of acid and Mn(III) turn-on fluorescent protein (FP) sensors, named iLovU, based on PET and the genetic incorporation of superior PET quenchers in the fluorescent flavoprotein iLov. Using the iLovU PET sensors, we monitored the cytoplasmic acidification process, and achieved Mn(III) fluorescence sensing for the first time. The iLovU sensors should be applicable for studying pH changes in living cells, monitoring biogentic Mn(III) in the environment, and screening for efficient manganese peroxidase, which is highly desirable for lignin degradation and biomass conversion. Our work establishes a platform for many more protein PET sensors, facilitates the de novo design of metalloenzymes harboring redox active residues, and expands our ability to probe protein conformational dynamics.

Monodisperse α-Fe(2)O(3)@SiO(2)@Au core/shell nanocomposite spheres: synthesis, characterization and properties.

A new hybrid spherical structure α-Fe(2)O(3)@SiO(2)@Au with a size of about 141 nm was designed, with a hematite cubic core surrounded by a thick silica shell and further decorated with gold nanoparticles. The monodisperse α-Fe(2)O(3)@SiO(2) spheres were first prepared by a sol-gel process based on the modified Stöber method. Subsequently, the surface of the α-Fe(2)O(3)@SiO(2) particles was functionalized by-NH(2) functional groups. The electrostatic attraction of -NH(2) groups will attach the negatively charged Au nanoparticles to the amino-functionalized α-Fe(2)O(3)@SiO(2) nanospheres in order to prepare α-Fe(2)O(3)@SiO(2) monodisperse hybrid spheres. The M(H) hysteresis loop for α-Fe(2)O(3)@SiO(2) and α-Fe(2)O(3)@SiO(2)@Au spheres indicates that the nanocomposite spheres exhibit superparamagnetic characteristics at room temperature. The optical properties and the application of these hybrid nanocomposites as catalysts for the conversion of CO to CO(2) have also been studied.