L-DNA, the mirror image of natural D-DNA, can be readily self-assembled into designer discrete or periodic nanostructures. The assembly products are characterized by polyacrylamide gel electrophoresis (PAGE), circular dichroism (CD) spectrum, atomic force microscope (AFM) and fluorescence microscope. We found that the use of enantiomer DNA as building material leads to the formation of DNA supra-molecules with opposite chirality. Therefore, the L-DNA self-assembly is a substantial complement to the structural DNA nanotechnology. Moreover, the L-DNA architectures feature superior nuclease resistance thus are appealing for in vivo medical applications.One of the central tasks of nanotechnology is to construct nano-scale structures with designed geometry, topology, and periodicity. Among various materials used to build designer nanoarchitectures, DNA distinguishes itself by its predictable Watson-Crick base-paring, structural stiffness and flexibility, ease to synthesize and biocompatibility. With a number of exciting breakthroughs in the past two decades, DNA based self-assembly has been recognized as one of the most efficient and reliable methods for bottom-up construction. 1-19 The success of DNA as a generic building material makes it appealing to involve other members of the nucleic acid family in nano-scale construction. For example, tecto-RNA motifs have been used to form square-shaped tiles that further self-assemble into finite or infinite sized twodimensional (2D) arrays. 20 Unnatural nucleic acids, such as locked nucleic acid (LNA) 21 and peptide nucleic acid (PNA), 22 have also been incorporated into self-assembled DNA structures. Recently, a four-arm junction motif was synthesized using glycol nucleic acid (GNA). 23 However, the structural (e.g. helical repeats and diameter), physical (e.g. thermal stability) and chemical properties (e.g. activity to intercalating fluorescent dyes) of these unnatural nucleic acid species are usually different from those of DNA, which adds extra design work and experimental uncertainty in the construction of more complicated nanostructures.Here we report the facile preparation of well-defined discrete, one-dimensional (1D) and twodimensional (2D) nanostructures using mirror-image DNA, L-DNA, the enantiomer of the natural DNA, D-DNA, by simply applying previously reported DNA self-assembly designs and protocols. As perfect mirror-images, L-DNA and D-DNA possess the same duplex conformation except for their opposite chirality. 24,25 They are physically and chemically identical to each other under non-chiral circumstances. Given a rich toolbox of DNA-tile motifs, 26-31 it is therefore a straight-forward and attractive idea to construct nanoarchitectures with L-DNA in substitution to the normally used D-DNA. Ideally, the geometry and periodicity of the resulting structures is expected to be identical to those composed of D-DNA. However, whether and how the difference in chirality of the DNA duplex is reflected on the E-mail: yan_liu@asu.edu; E-mail: hao.yan@asu.edu....

Background The systemic low‐frequency oscillation (sLFO) functional (f)MRI signals extracted from the internal carotid artery (ICA) and the superior sagittal sinus (SSS) are found to have valuable physiological information. Purpose 1) To further develop and validate a method utilizing these signals to measure the delay times from the ICAs and the SSS. 2) To establish the delay time as an effective perfusion biomarker that associates with cerebral circulation time (CCT). 3) To explore within subject variations, and the effects of gender and age on the delay times. Study Type Prospective. Subjects In all, 100 healthy adults (Human Connectome Project [HCP], age range 22–36 years, 54 females and 46 males), 56 healthy children (Adolescent Brain Cognitive Development project) were included. Field Strength/Sequence Echo planar imaging (EPI) sequence at 3T. Assessment The sLFO fMRI signals from the ICAs and the SSSs were extracted from the resting state fMRI data. The maximum cross‐correlation coefficients and their corresponding delay times were calculated. The gender and age differences of delay times were assessed statistically. Statistical Tests T‐tests were conducted to measure the gender differences. The Kruskal–Wallis test was used to detect age differences. Results Consistent and robust results were found from 80% of the 400 HCP scans included. Negative correlations (–0.67) between the ICA and the SSS signals were found with the ICA signal leading the SSS signal by ∼5 sec. Within subject variation was 2.23 sec at the 5% significance level. The delay times were not significantly different between genders (P = 0.9846, P = 0.2288 for the left and right ICA, respectively). Significantly shorter delay times (4.3 sec) were found in the children than in the adults (P < 0.01). Data Conclusion We have shown that meaningful perfusion information (ie, CCT) can be derived from the sLFO fMRI signals of the large blood vessels. Level of Evidence: 1 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2019;50:1504–1513.

Elevated carbon dioxide (CO2) in breathing air is widely used as a vasoactive stimulus to assess cerebrovascular functions under hypercapnia (i.e., “stress test” for the brain). Blood-oxygen-level-dependent (BOLD) is a contrast mechanism used in functional magnetic resonance imaging (fMRI). BOLD is used to study CO2-induced cerebrovascular reactivity (CVR), which is defined as the voxel-wise percentage BOLD signal change per mmHg change in the arterial partial pressure of CO2 (PaCO2). Besides the CVR, two additional important parameters reflecting the cerebrovascular functions are the arrival time of arterial CO2 at each voxel, and the waveform of the local BOLD signal. In this study, we developed a novel analytical method to accurately calculate the arrival time of elevated CO2 at each voxel using the systemic low frequency oscillations (sLFO: 0.01-0.1 Hz) extracted from the CO2 challenge data. In addition, 26 candidate hemodynamic response functions (HRF) were used to quantitatively describe the temporal brain reactions to a CO2 stimulus. We demonstrated that our approach improved the traditional method by allowing us to accurately map three perfusion-related parameters: the relative arrival time of blood, the hemodynamic response function, and CVR during a CO2 challenge.

Genetic alterations of ␣-actinin-4 can cause podocyte injury through multiple mechanisms. Although a mechanism involving gain-of-␣-actinin-4 function was well described and is responsible for a dominantly inherited form of human focal segmental glomerulosclerosis (FSGS), evidence supporting mechanisms involving loss-of-␣-actinin-4 function in human glomerular diseases remains elusive. Here we show that ␣-actinin-4 deficiency occurs in multiple human primary glomerulopathies including sporadic FSGS, minimal change disease, and IgA nephropathy. Furthermore, we identify a close correlation between the levels of ␣-actinin-4 and CLP36, which form a complex in normal podocytes, in human glomerular diseases. siRNA-mediated depletion of ␣-actinin-4 in human podocytes resulted in a marked reduction of the CLP36 level. Additionally, two FSGS-associated ␣-actinin-4 mutations (R310Q and Q348R) inhibited the complex formation between ␣-actinin-4 and CLP36. Inhibition of the ␣-actinin-4-CLP36 complex, like loss of ␣-actinin-4, markedly reduced the level of CLP36 in podocytes. Finally, reduction of the CLP36 level or disruption of the ␣-actinin-4-CLP36 complex significantly inhibited RhoA activity and generation of traction force in podocytes. Our studies reveal a critical role of the ␣-actinin-4-CLP36 complex in podocytes and provide an explanation as to how ␣-actinin-4 deficiency or mutations found in human patients could contribute to podocyte defects and glomerular failure through a lossof-function mechanism.Chronic and end stage kidney diseases, which are frequently caused by defects in glomerular filtration barrier function, have become a major global health problem. Although many factors can contribute to the development and progression of human glomerulopathies, genetic defects play important roles in the disease processes (1-6). Elucidation of how genetic alterations contribute to glomerular defects is therefore critical for understanding the molecular mechanisms underlying the development and progression of human glomerulopathies.The glomerular filtration barrier is composed of an endothelium, a glomerular basement membrane, and a layer of podocytes building the slit diaphragm for filtration with their interdigitating foot processes. Although genetic alterations can cause defects in any of the three layers of the glomerular filtration barrier, podocytes appear to be a frequent target of genetic alterations in glomerulopathies (3, 4, 7-14). ␣-Actinin-4 is a member of the actinin protein family that consists of an actinbinding domain in the N terminus, four spectrin-like repeats in the central region, and two EF-hand motifs in the C terminus (15). Although both ␣-actinin-1 and -4 are expressed in mouse podocytes, ␣-actinin-4 is the sole member of the actinin family expressed in human podocytes (16). ␣-Actinin-4 is widely expressed in mammalian tissues and organs. However, despite the widespread expression, podocytes appear to be the primary site of manifestations of diseases induced by genetic alterations of ACTN4 (16,...

The synthesis of poly(2,6‐dimethyl‐1,4‐phenylene oxide) with one 2,6‐dimethylphenol chain end (PPO–OH) and with well‐defined molecular weight by phase transfer catalyzed polymerization of 4‐bromo‐2,6‐dimethylphenol (20) in the presence of either 2,4,6‐trimethylphenol (1) or 4‐t‐butyl‐2,6‐dimethylphenol (1′) as chain initiators is described. The range of controllable molecular weights and the mechanism of molecular weight control are discussed based on the differences between the reactivities of 20, 1, and 1′ and of the corresponding reactive species. The PPO–OH synthesized from 20/1′ has structural units derived from 1′ attached only at the chain end. PPO–OH synthesized from 20/1 contains structural units derived from 1 both internally and at the chain ends. Structural units derived from side reactions were identified by 1H‐NMR spectroscopy. A reaction mechanism is proposed to account for their formation.

SYNOPSISThe synthesis and the oxidative polymerization of 1,5-bis (phenoxy )pentane, 1,5bis (phenoxy )pentane substituted with various electron-donating groups, and 1,5bis (pheny1thio)pentane is described. The polymers derived from methyl substituted 1,5bis (phenoxy )pentane monomers contain diphenyl methane, 1,2-diphenylethane, and benzyl chloride structural units. The mechanism for the generation of these structural units is presented. It consists of the proton transfer reactions from the cation-radical propagating species and subsequent reactions of the resulting benzyl radicals. The polymerizability of monomers with 1,5-pentanedioxy group is lower than that of the monomers with diphenyl sulfone group. This dissimilarity was attributed to the difference between both the reactivity and the concentration of the cation-radical propagating species resulted from these two classes of monomers. Keywords: Scholl reaction cation-radical polymerization 1,5-bis (phen0xy)pentanes polymerization mechanism polymerizability of monomers proton transfer reactions * Part VII: V. Percec, J. H. Wang, and S. Okita, J. Polym. A: Polym. Chem., 29, 1789 (1991). + 1 2 RO OR 23 23 -2n' 23 -RO OR 22 Scheme 4. nism. Sci. PartThe cation-radical polymerization mecha-

The degradation and stability of biodegradable lms determine the service length of mulch lms in actual use. Most biodegradable polymers degrade too fast to meet the required durability of mulch lms. The objective of this work is to investigate the degradation behaviors of poly(butylene adipate-coterephthalate) (PBAT) /polyhydroxyalkanoate (PHA) blend mulch lms. Several different types of stabilizers were incorporated in the biodegradable blends to provide protection for the PHA/PBAT lms during thermal processing and aging on agricultural elds. The degradation process of the lms was systematically studied under an Accelerated Aging Test (AAT) and a Soil Aging Test (SAT). Adding a light stabilizer, UV stabilizer, or antioxidant to the mulch lms led to signi cant improvement in the retention of mechanical properties of the lms under both AAT and SAT. Morphological evolution of the lms with or without a UV stabilizer as a function of aging times was studied by Scanning Electron Microscopy (SEM).The results of thermal properties and crystallinity revealed damage of crystal structure of the lms during AAT. Spectrocopic results indicated that the lms underwent both hydrolysis and photodegradative chain scissions (Norrish Type I/II reactions and photo-oxidation). The degradation mechanisms of the PHA/PBAT biodegradable mulch lms were proposed.

Polyether sulfones containing perfluoroalkyl segments were prepared by room temperature radical‐cation polymerization (Scholl reaction) of 1,4‐bis[4‐(1‐napthoxy)phenylsulfonyl]perfluorobutane (1a) and 1,8‐bis [4‐(1‐napthoxy) phenylsulfonyl] perfluoroctane (1b) in nitrobenzene, using anhydrous ferric chloride as oxident. The homopolymerization of 1a and of 1b performed under various polymerization conditions, resulted in polymers with number average molecular weight (M̄n) up to 33,000 and 38,000 g/mol, respectively. Copolymerization of the fluorinated monomers 1a with 1b, and either 1a or 1b with 4,4′‐bis(1‐naphthoxy) diphenyl sulfone (4) and 1,5‐bis (1‐naphthoxy) pentane (5) produced copolymers of M̄n up to 18,100 g/mol. The reactivity of the various monomers was discussed on the basis of the induction and resonance stabilization effects.