The use of animal organs could potentially alleviate the critical worldwide shortage of donor organs for clinical transplantation. Because of the strong immune response to xenografts, success will probably depend upon new strategies of immune suppression and induction of tolerance. Here we report our initial results using alpha-1,3-galactosyltransferase knockout (GalT-KO) donors and a tolerance induction approach. We have achieved life-supporting pig-to-baboon renal xenograft survivals of up to 83 d with normal creatinine levels.

Crystalline structure and molecular dynamics in α and α′ crystals of poly(L-lactide) (PLLA) and PLLA/poly(Dlactide) (PDLA) stereocomplex (sc) crystals have been investigated by the temperature-variable FTIR and solid-state 13 C CP-MAS NMR spectroscopy. The crystal forms of polylactide (PLA) have different band frequencies, correlation field splittings in FTIR spectra and different line shapes, and resonance splittings in solid-state NMR spectra, which become more distinct with cooling to the cryogenic conditions. The well-resolved splittings in NMR resonances of α crystals, attributable to the crystallographically inequivalent sites within crystal unit cell, are considered to be due to the dipolar interactions related to the carbonyl, methyl, and methine groups. The splittings in FTIR bands and NMR resonances are absent in α′ crystals, indicating the disordered conformation and loose molecular lateral packing within their crystal lattices. The significant FTIR frequency shifts of ν(CO), ν(CH 3 ), and ν(CH) modes during stereocomplex crystallization of PLLA/PDLA blend and the appearance of spectral splittings at cryogenic conditions suggest the coexistence of weak C−H···OC hydrogen bonds and dipolar interactions between PLLA and PDLA chains in the sc crystals of PLA. Below the glass transition temperature (T g ), the spin−lattice relaxation times of PLA with different crystalline structures increase in the order of amorphous ≈ α′ < α < sc.

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The molecular structure and dynamics of regioregulated poly͑3-butylthiophene͒ ͑P3BT͒, poly͑3-hexylthiophene͒ ͑P3HT͒, and poly͑3-dodecylthiophene͒ ͑P3DDT͒ were investigated using Fourier-transform infrared absorption ͑FTIR͒, solid-state 13 C nuclear-magnetic resonance ͑NMR͒, and differential-scanning calorimetry ͑DSC͒ measurements. In the DSC measurements, the endothermic peak was obtained around 340 K in P3BT, and assigned to enthalpy relaxation that originated from the glass transition of the thiophene-ring twist in crystalline phase from results of FTIR, 13 C cross-polarization and magic-angle spinning ͑CPMAS͒ NMR, 13 C spin-lattice relaxation-time measurements, and centerband-only detection of exchange ͑CODEX͒ measurements. We defined this transition as a twist-glass transition, which is analogous to the plastic crystal-glassy crystal transition.

Electric double-layer capacitors are efficient energy storage devices that have the potential to account for uneven power demand in sustainable energy systems. Earlier attempts to improve an unsatisfactory capacitance of electric double-layer capacitors have focused on meso- or nanostructuring to increase the accessible surface area and minimize the distance between the adsorbed ions and the electrode. However, the dielectric constant of the electrolyte solvent embedded between adsorbed ions and the electrode surface, which also governs the capacitance, has not been previously exploited to manipulate the capacitance. Here we show that the capacitance of electric double-layer capacitor electrodes can be enlarged when the water molecules are strongly confined into the two-dimensional slits of titanium carbide MXene nanosheets. Using electrochemical methods and theoretical modeling, we find that dipolar polarization of strongly confined water resonantly overscreens an external electric field and enhances capacitance with a characteristically negative dielectric constant of a water molecule.

The enhancement effect of nucleation in immiscible blend systems has recently attracted interest. Although several authors have reported that the effect occurs at the phase interface, little is known about the mechanism involved. We focused on poly(L-lactide) (PLLA)/poly(ɛ-caprolactone) (PCL) immiscible blend systems in which the presence of PCL enhanced the nucleation of PLLA at low temperature. We investigated the nucleation behavior of PLLA during aging at temperatures below T g . Generally, neat polymers, including PLLA, seldom generate nuclei below T g due to restrictions in chain mobility. However, through DSC analysis of the crystallization behavior following an aging process, we revealed that the nucleation of PLLA occurs during aging even at temperatures below T g in the PLLA/PCL blend. Since the nuclei density became saturated with increasing aging time, the nucleation behavior was regarded as heterogeneous nucleation. The asymptotic density of nuclei depended on the PCL content, indicating that dispersed PCL acted as active sites for nucleation. The nucleation rate R was almost independent of the aging temperature, suggesting that the marked decrease in chain mobility due to the glass transition is locally evaded at the active sites. Nucleation was observed even at temperatures as much as 40 °C lower than T g following the addition of only 1 wt % PCL, while the T g obtained by a DSC heating scan showed a subtle decrease. This suggests that the limited miscibility of PLLA/PCL leads to the aggregation of PCL and induces local and deep depression of T g at the interface of the PCL domains, resulting in marked enhancement of PLLA nucleation.

ABSTRACT:We have previously suggested that crystalline Bombyx mori silk in silk 16 II form (the silk structure after spinning) is not a simple antiparallel β-sheet but is 17 intrinsically heterogeneous. Using the peptide (AG) 15 36 and dried under mild conditions) has been shown to possess a 37 repeated type II β-turn structure. 7−9 On the other hand, the 38 precise intermolecular packing in the Silk II form (representing 39 the core of the spun silk fiber) has not yet been determined. 40 Using X-ray fiber diffraction of the crystalline region, the 41 structure of Silk II was first characterized by Marsh, Corey, and 42 Pauling 10 as a regular array of antiparallel β-sheets: this 43 structure remains the classic image of β-sheet silk. We call this 44 cxs00 | ACSJCA | JCA10.0.1465/W Unicode | research.3f (R3.6.i5 HF05:4232 | 2.0 alpha 39) 2014/10/10 09:17:00 | PROD-JCA1 | rq_3109040 | 12/15/2014 13:54:33 | 9 | JCA-DEFAULT 65 using a small (Ala-Gly) 15 peptide as the model. The alternating 66 copolypeptide (Ala-Gly) n has been generally accepted as a good 67 model of the crystalline region, NMR spectra of (AG) n 68 correspond closely to those obtained using the crystalline 69 fraction of native silk II fibers, 7−16 and the torsion angles of the 70 straight backbone chains correspond to the typical angles of an 71 antiparallel β-sheet. 17 In previous 13 C solid state NMR studies 72 of (AG) n , the 13 Cβ signal of the Ala residues has been reported 73 to consist of three peaks. 15,16 The high-field peak was assigned 74 to a distorted β-turn/random coil, while the other two peaks 75 were assigned to antiparallel β-sheet structures with different 76 intermolecular arrangements. The key challenge lies in the ability to discern and resolve the 92 two kinds of antiparallel β-sheet chains with different 93 intermolecular packing arrangements, as detected here and in 94 the earlier 13 C CP/MAS NMR study. 15,16 We therefore carried 95 out a search of packing arrangements, guided by crystallo-96 graphic and NMR data; refined the resulting structures; and 97 tested them against experimental data. The peptide (AG) n 98 crystallizes in space group P2 1 , a rectangular unit cell with the 99 parameters a = 9.38 Å, b = 9.49 Å, and c = 6.98 Å. The Marsh 100 model places the molecular axis along b but is otherwise very 101 similar: a = 9.40 Å, b = 6.97 Å, and c = 9.20 Å. In order to 102 generate two kinds of β-sheet models with different 103 intermolecular arrangements, we had the idea to calculate 104 atomic coordinates for the chains, setting either c or b along the 105 molecular axis. For each of these two models, energy 106 optimization was performed. 9 1 H, 13 C, and 15 N chemical shifts 107 were then predicted for the two antiparallel β-sheet structures 108 using the GIPAW method. 23

The glass transition and physical aging processes of poly(L-lactide) (PLLA) were studied by variable-temperature Fourier transform infrared (FTIR) spectroscopy and (13)C solid-state NMR spectroscopy. The glass transition temperature (T(g)) of PLLA can be well determined from the temperature-dependent FTIR intensity. Nearby T(g), a distinct change in the slope of spectral intensity versus temperature plot is detected. FTIR results suggest that the energy-favorable gauche-trans (gt) conformers rearrange into the less energy-favorable gauche-gauche (gg) counterparts with heating over the glass transition region, which becomes more distinct at temperature above T(g). Besides, the 1267 cm(-1) band, which shows different trends of variation from the other bands upon heating, was assigned to be more sensitive to the nu(as)(C-O-C)+delta(CH) vibration mode of the less energy-favorable gg conformers in PLLA. By comparing the FTIR spectra of the aged and deaged PLLA, it was demonstrated that the rearrangement from the high- to low-energy conformers, i.e., gg to gt, occurs with physical aging. (13)C spin-lattice relaxation measurements indicate that the relaxation rate distribution broadens with aging, which agrees with the previous suggestion that the locally ordered domains are formed during physical aging. Because of the larger variation in the conformational state and microstructure, the FTIR intensities vary much more abruptly for the aged sample with heating to nearby T(g).