Elevated uptake of Th and U by netted chain fern (<Emphasis Type="Italic">Woodwardia areolata</Emphasis>)

We assessed the ability of netted chain fern (Woodwardia areolata) to uptake U and Th from wetland soils on the U.S. Department of Energy’s Savannah River Site in South Carolina. Netted chain fern had the highest Th and U concentrations of all plants collected from the wetland. Ferns grown in contaminated soil (329 mg·kg⁻¹ Th, 44 mg·kg⁻¹ U) in a greenhouse contained 6.4 mg·kg⁻¹ Th and 5.3 mg·kg⁻¹ U compared with 0.13 mg·kg⁻¹ Th and 0.035 mg·kg⁻¹ U in Bermuda grass (Cynodon dactylon). Netted chain fern has potential for the phytoremediation of soils contaminated with Th and U.     

Withanolides from Aureliana fasciculata var. fasciculata

In the first phytochemical study of the Aureliana genus (Solanaceae), two new withanolides, 1 and 2 , together with two known sterols, were isolated from the MeOH extract of the leaves of Aureliana fasciculata var. fasciculata. The structures were established as (4S,22R)‐16α‐acetoxy‐5β,6β‐epoxy‐4β,17α‐dihydroxy‐1‐oxowitha‐2,24‐dienolide (aurelianolide A) and (4S,22R)‐16α‐acetoxy‐4β,17α‐dihydroxy‐1‐oxowitha‐2,5,24‐trienolide (aurelianolide B). The new compounds possessed the unusual 16α,17α‐dioxygenated group and were fully characterized by spectroscopic techniques, including ¹H‐ and ¹³C‐NMR (DEPT), as well as 2D‐NMR (HMBC, HMQC, ¹H,¹H‐COSY, NOESY) experiments, and HR‐MS.     

Green Process to Prepare Silk Fibroin/Gelatin Biomaterial Scaffolds

A new all‐aqueous and green process is described to form three‐dimensional porous silk fibroin matrices with control of structural and morphological features. Silk‐based scaffolds are prepared using lyophilization. Gelatin is added to the aqueous silk fibroin solution to change the silk fibroin conformation and silk fibroin–water interactions through adjusting the hydrophilic interactions in silk fibroin–gelatin–water systems to restrain the formation of separate sheet like structures in the material, resulting in a more homogenous structure. Water annealing is used to generate insolubility in the silk fibroin–gelatin scaffold system, thereby avoiding the use of organic solvents such as methanol to lock in the β‐sheet structure. The adjusting of the concentration of gelatin, as well as the concentration of silk fibroin, leads to control of morphological and functional properties of the scaffolds. The scaffolds were homogeneous in terms of interconnected pores, with pore sizes ranging from 100 to 600 µm, depending on the concentration of silk fibroin used in the process. At the same time, the morphology of the scaffolds changed from lamellar sheets to porous structures based on the increase in gelatin content. Compared with salt‐leaching aqueous‐derived scaffolds and hexafluoroisopropanol (HFIP)‐derived scaffolds, these freeze‐dried scaffolds had a lower content of β‐sheet, resulting in more hydrophilic features. Most of gelatin was entrapped in the silk fibroin–gelatin scaffolds, without the burst release in PBS solution. During in vitro cell culture, these silk fibroin–gelatin scaffolds had improved cell‐compatibility than salt‐leaching silk fibroin scaffolds. This new process provides useful silk fibroin‐based scaffold systems for use in tissue engineering. Furthermore, the whole process is green, including all‐aqueous, room temperature and pressure, and without the use of toxic chemicals or solvents, offering new ways to load bioactive drugs or growth factors into the process.

     

Role of Polyalanine Domains in β‐Sheet Formation in Spider Silk Block Copolymers

Genetically engineered spider silk‐like block copolymers were studied to determine the influence of polyalanine domain size on secondary structure. The role of polyalanine block distribution on β‐sheet formation was explored using FT‐IR and WAXS. The number of polyalanine blocks had a direct effect on the formation of crystalline β‐sheets, reflected in the change in crystallinity index as the blocks of polyalanines increased. WAXS analysis confirmed the crystalline nature of the sample with the largest number of polyalanine blocks. This approach provides a platform for further exploration of the role of specific amino acid chemistries in regulating the assembly of β‐sheet secondary structures, leading to options to regulate material properties through manipulation of this key component in spider silks.

     

Transfer measurements for the Ti+Ni systems at near barrier energies

Large enhancements have been observed in the sub-barrier fusion cross sections for Ti+Ni systems in our previous studies. Coupled channel calculations incorporating couplings to 2⁺ and 3⁻ states failed to explain these enhancements completely. A possibilty of transfer channels contributing to the residual enhancements had been suggested. In order to investigate the role of relevant transfer channels, measurements of one- and two-nucleon transfer were carried out for ^46,48Ti+⁶¹Ni systems. The present paper gives the results of these studies.     

The structure of plasma-polymerized toluene: A solid-state 13C-NMR study of isotopically labeled polymers

A detailed magic angle spinning ¹³C-NMR investigation of the intractable polymer prepared by plasma polymerization of toluene and isotopically labeled toluene led to a proposed model for the structure of the polymer and suggested some of the likely processes that occur in the gas phase leading to film formation. From the ¹³C spectra four resolved resonances permitted the determination of the contribution of nonprotonated and protonated unsaturated as well as methyl and other aliphatic carbons to the polymer structure. Specific ¹³C isotopic labeling of the methyl and phenyl C-1 toluene carbons in the injected liquid vapor allowed the destination of these carbons in the deposited polymer to be traced. The dominant structure is derived primarily from two precursors: benzyl radical and toluene itself. The ¹³C data further requires a net saturation of ca. 30% of the toluene double bonds and a net displacement of hydrogen by carbon on ca. 20% of the toluene ring carbons.