SummaryBarley ( Hordeum vulgare L.), genetically modified with the Al 3+ resistance gene of wheat ( TaALMT1 ), was compared with a non-transformed sibling line when grown on an acidic and highly phosphate-fixing ferrosol supplied with a range of phosphorus concentrations.In short-term pot trials (26 days), transgenic barley expressing TaALMT1 (GP-ALMT1) was more efficient than a non-transformed sibling line (GP) at taking up phosphorus on acid soil, but the genotypes did not differ when the soil was limed. Differences in phosphorus uptake efficiency on acid soil could be attributed not only to the differential effects of aluminium toxicity on root growth between the genotypes, but also to differences in phosphorus uptake per unit root length. Although GP-ALMT1 out-performed GP on acid soil, it was still not as efficient at taking up phosphorus as plants grown on limed soil. GP-ALMT1 plants grown in acid soil possessed substantially smaller rhizosheaths than those grown in limed soil, suggesting that root hairs were shorter. This is a probable reason for the lower phosphorus uptake efficiency. When grown to maturity in large pots, GP-ALMT1 plants produced more than twice the grain as GP plants grown on acid soil and 80% of the grain produced by limed controls. Expression of TaALMT1 in barley was not associated with a penalty in either total shoot or grain production in the absence of Al 3+ , with both genotypes showing equivalent yields in limed soil. These findings demonstrate that an important crop species can be genetically engineered to successfully increase grain production on an acid soil.

Juvenile hormones (JH) are a class of regulatory sesquiterpenoids that control metamorphosis in immature insects and reproduction in adult insects. The regulation of JH synthesis by the corpora allata (CA), a pair of endocrine glands with nervous connections to the brain, is achieved by a complex interplay of stimulatory and inhibitory factors mediated in part by the brain. The neuropeptide, allatotropin (Mas AT), was recently isolated and sequenced from the brain of the tobacco hornworm Manduca sexta. Mas AT is a 13-residue amidated peptide that activates JH synthesis in adult, but not larval, lepidopteran CA. A 23-nucleotide degenerate oligonucleotide was designed based on the peptide sequence and was used to isolate the Mas AT genomic clone. The Mas AT gene is expressed as three mRNAs which differ from one another by alternative splicing. These mRNAs are predicted to encode three distinct prohormones, each containing Mas AT. A restriction fragment from the genomic clone was then used to isolate the cDNA clone. In situ hybridization and immunohistochemistry studies show that Mas AT is expressed in both the central and enteric nervous systems. Cells expressing Mas AT were identified in the brain, frontal ganglion and terminal ganglion.

Elastin-like polypeptides (ELPs) are thermoresponsive biopolymers that undergo an LCST-like phase transition in aqueous solutions. The temperature of this LCST-like transition, T t , can be tuned by varying the number of repeat units in the ELP, sequence and composition of the repeat units, the solution conditions, and via conjugation to other biomacromolecules. In this study, we show how and why the choice of guest (X) residue in the VPGXG pentad repeat tunes the T t of short ELPs, (VPGXG) 4 , in the free state and when conjugated to collagen-like peptides (CLPs). In experiments, the (VPGWG) 4 chain (in short, WWWW) has a T t < 278 K, while (VPGFG) 4 or FFFF has a T t > 353 K in both free ELP and ELP−CLP systems. The T t for the FWWF ELP sequence decreases from being >353 K for free ELP to <278 K for the corresponding ELP−CLP system. The decrease in T t upon conjugation to CLP has been shown to be due to the crowding of ELP chains that decreases the entropic loss upon ELP aggregation. Even though the net hydrophobicity of ELP has been reasoned to drive the T t , the origins of lower T t of WWWW compared to FFFF are unclear, as there is disagreement in hydrophobicity scales in how phenylalanine (F) compares to tryptophan (W). Motivated by these experimental observations, we use a combination of atomistic and coarse-grained (CG) molecular dynamics simulations. Atomistic simulations of free and tethered ELPs show that WWWW are more prone to acquire β-turn structures than FFFF at lower temperatures. Also, the atomistically informed CG simulations show that the increased local stiffness in W than F due to the bulkier side chain in W compared to F, alone does not cause the shift in the transition of WWWW versus FFFF. The experimentally observed lower T t of WWWW than FFFF is achieved in CG simulations only when the CG model incorporates both the atomistically informed local stiffness and stronger effective attractions localized at the W position versus the F position. The effective interactions localized at the guest residue in the CG model is guided by our atomistically observed increased propensity for β-turn structure in WWWW versus FFFF and by past experimental work of Urry et al. quantifying hydrophobic differences through enthalpy of association for W versus F.

This study uses simulations and experiments to explain why and how the placement of tyrosine residues in elastin-peptide containing conjugates impacts their transition temperature.

Peptide–polymer conjugates are a class of soft materials composed of covalently linked blocks of protein/polypeptides and synthetic/natural polymers. These materials are practically useful in biological applications, such as drug delivery, DNA/gene delivery, and antimicrobial coatings, as well as nonbiological applications, such as electronics, separations, optics, and sensing. Given their broad applicability, there is motivation to understand the molecular and macroscale structure, dynamics, and thermodynamic behavior exhibited by such materials. We focus on the past and ongoing molecular simulation studies aimed at obtaining such fundamental understanding and predicting molecular design rules for the target function. We describe briefly the experimental work in this field that validates or motivates these computational studies. We also describe the various models (e.g., atomistic, coarse-grained, or hybrid) and simulation methods (e.g., stochastic versus deterministic, enhanced sampling) that have been used and the types of questions that have been answered using these computational approaches.

Polyvinyl acetate precipitates from aqueous solution as it is formed. When potassium persulphate is used as initiator the polymer suspension is stable and constitutes the principal locus of reaction. The effect of reaction conditions on the rate of polymerization and on the number of particles formed ha5 been studied. The surface charge density appears to be the factor which determines the number of particles formed and which limits the rate of reaction.ZUSAMMENFASSUNG:Polyvinylacetat f a t bei seiner Bildung aus wainriger Losung aus. Bei Verwendung von Kaliumpersulfat als Initiator ist die Polymersuspension bestandig und stellt den hauptsachlichen Ort der Reaktion dar. Der Eidul3 der Reaktionsbedingungen auf die Polymerisationsgeschwindigkeit und auf die Zahl der sich bildenden Polymerteilchen wird untersucht. Es scheint, dal3 die Oberflachedadungsdichte die Zahl der Polymerteilchen bestimmt und auch die Reaktionsgeschwindigkeit begenzt.

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Synergistic approach of experiments and simulations to design multifunctional collagen mimetic peptides relevant for the creation of nanostructured soft materials.