Incorporation of N-heterocyclic cations into proteins with a highly directed chemical modification

N-Heterocyclic cations are incorporated into proteins using 5-(2-bromoethyl)phenanthridinium bromide, which selectively reacts with either cysteine or lysine residues, resulting in ethylphenanthridinium (Phen) or highly stable cyclised dihydro-imidazo-phenanthridinium (DIP) adducts respectively; these modifications have been found to manipulate the observed structure of lysozyme and bovine serum albumin by AFM.     

Dilute-sulfuric acid pretreatment of corn stover in pilot-scale reactor

Corn stover is a domestic feedstock that has potential to produce significant quantities of fuel ethanol and other bioenergy and biobased products. However, comprehensive yield and carbon mass balance information and validated kinetic models for dilute-sulfuric acid (H₂SO₄) pretreatment of corn stover have not been available. This has hindered the estimation of process economics and also limited the ability to perform technoeconomic modeling to guide research. To better characterize pretreatment and assess its kinetics, we pretreated corn stover in a continuous 1 t/d reactor. Corn stover was pretreated at 20% (w/w) solids concentration over a range of conditions encompassing residence times of 3–12 min, temperatures of 165–195°C, and H₂SO₄ concentrations of 0.5–1.4% (w/w). Xylan conversion yield and carbon mass balance data were collected at each run condition. Performance results were used to estimate kinetic model parameters assuming biphasic hemicellulose hydrolysis and a hydrolysis mechanism incorporating formation of intermediate xylo-oligomers. In addition, some of the pretreated solids were tested in a simultaneous saccharification and fermentation (SSF) process to measure the reactivity of their cellulose component to enzymatic digestion by cellulase enzymes. Monomeric xylose yields of 69–71% and total xylose yields (monomers and oligomers) of 70–77% were achieved with performance level depending on pretreatment severity. Cellulose conversion yields in SSF of 80–87% were obtained for some of the most digestible pretreated solids.     

Enzyme production, growth, and adaptation of T. reesei strains QM9414, L-27, RL-P37, and rut C-30 to conditioned yellow poplar sawdust hydrolysate

National Renewable Energy Laboratory (NREL) has developed a conditioning process that decreases acetic acid levels in pretreated yellow poplar hydrolysate. Trichoderma reesei is sensitive to acetic acid and this conditioning method has enabled applied cellulase production with hardwoods. T. reesei strains QM9414, L-27, RL-P37, and Rut C-30 were screened for growth on conditioned hydrolysate liquor. Tolerance to hydrolysate was found to be strain-dependent. Strain QM9414 was adapted to grow in 80% (v/v) conditioned hydrolysate (40 g/L of soluble sugars and 1.6 g/L acetic acid from pretreated poplar). However, enzyme production was highest at 20% (v/v) hydrolysateusing strain L-27. Cellulasetiters of 2–3 International Filter Paper Units (IFPU)/mL were achieved using pretreated yellow poplar liquors and solids as the sole carbon sources.     

High pressure effects on liquid viscosity and glass transition behaviour,polyamorphic phase transitions and structural properties of glasses and liquids

Since the pioneering work of Bridgman it has been known that pressure affects the glass transition of polymers and liquid state viscosities. Usually the T_g and viscosity both increase as a function of pressure as expected from ‘free volume’ theories. However, H₂O provided a notable exception in that the viscosity passes through a minimum at low temperature. It was thought that this might be linked to the anomalous thermal expansion behavior. However further research on geologically important aluminosilicate liquids revealed that they could show anomalous viscosity decreases with increasing pressure and this behavior is given a structural interpretation as five-fold coordinated Si⁴⁺ and Al³⁺ species are formed. Also the existence of polyamorphism or density-driven liquid–liquid phase transitions in certain systems can lead to anomalies in the T_g or η vs. P relations. This may be the case for H₂O, for example. Current research is focusing on investigating structural changes in liquids and glasses at high pressure as the rich variety of behavior is becoming recognized. Both experimental studies and computer simulations are important as the underlying phenomonology is linked to changes in the glass or liquid structure as a function of densification.     

Water-soluble amorphous alumina-based ceramic precursors and alumosols: Structural and chemical characterization

We examined the solid-state water-soluble amorphous precursors that are formed by partial thermal decomposition of Al(NO₃)₃·9H₂O (aluminum nitrate nonahydrate: ANN) using Raman and FTIR and solid-state magic-angle spinning NMR spectroscopy. We also studied the species formed in the aqueous alumosols formed by dissolution of the pre-ceramic precursors using ²⁷Al NMR spectroscopy. Species identified in the alumosols included the Al³⁺(H₂O)₆ monomer, the [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺(Al₁₃) Keggin ion, and the Al₃₀ polycation, [Al₃₀O₈(OH)₅₆(H₂O)₂₄]¹⁸⁺, as well as various other oligomers or nanoparticles containing IV-, V- and VI-coordinated Al³⁺ ions.     

Infrared and millimeter-wave sensors for military special operations and law enforcement applications

We consider the application of infrared and millimeter-wave sensors, developed for the most part during the Cold War, to the solution of problems encountered by military special operations units and law enforcement personnel. These problems include detection of weapons concealed beneath clothing, through-the-wall surveillance, and wide-area surveillance under poor lighting conditions. Key sensors used in these applications are infrared cameras, millimeter-wave passive and active cameras, and millimeter-wave real-aperture and holographic radars. This paper discusses each type of sensor, describes its operation, and gives an example of its output, except in those cases where the device is early in its development phase and thus no outputs are available. All of these sensors form images, but the images are of varying quality. We conclude with a brief discussion of methods of using multiple sensors to improve performance.N. C. Currie and R. W. McMillan are permanently employed by the Georgia Institute of Technology, Georgia Tech Research Institute. They are working at Rome Laboratory supported by the Air Force Office of Scientific Research University Resident Research Program.     

Mn[III] uroporphyrin I: a novel metalloporphyrin contrast agent for magnetic resonance imaging.

We have used an intracranial 9L rat brain tumor model to determine whether a novel metalloporphyrin, Mn[III] uroporphyrin I (MnUROP-I), could function as an intravenous MRI contrast agent for brain tumors. In several experiments, 24 male Fischer 344 rats were inoculated intracranially with 9L brain tumor cells. On day 15 postinoculation, animals were anesthetized and the femoral vein exposed. Prior to the intravenous injection of the contrast agent, a precontrast scan (1 Tesla in a standard head coil) was performed. Thirty min after injection of the contrast agent, a postcontrast scan was performed. Although there was only a suggestion of abnormality on the precontrast scans, the presence of tumor was visibility enhanced in the postcontrast scans. In 3 animals scanned at 24 hr postinjection, persistent tumor enhancement was demonstrated. Measured tumor sizes on the MRI scans were consistent with sizes measured at autopsy and histologically. These results demonstrate that MnUROP-I is an effective MRI contrast agent for the detection of an intracranial brain tumor in the rat model.     

Min-max game theory and algebraic Riccati equations for boundary control problems with continuous input-solution map. Part II: The general case

We consider the abstract dynamical framework of [LT3, class (H.2)] which models a variety of mixed partial differential equation (PDE) problems in a smooth bounded domain ⁿ , arbitraryn, with boundaryL ₂-control functions. We then set and solve a min-max game theory problem in terms of an algebraic Riccati operator, to express the optimal quantities in pointwise feedback form. The theory obtained is sharp. It requires the usual Finite Cost Condition and Detectability Condition, the first for existence of the Riccati operator, the second for its uniqueness and for exponential decay of the optimal trajectory. It produces an intrinsically defined sharp value of the parameter, here called _c (critical), _c0, such that a complete theory is available for > _c, while the maximization problem does not have a finite solution if 0 < < _c. Mixed PDE problems, all on arbitrary dimensions, except where noted, where all the assumptions are satisfied, and to which, therefore, the theory is automatically applicable include: second-order hyperbolic equations with Dirichlet control, as well as with Neumann control, the latter in the one-dimensional case; Euler-Bernoulli and Kirchhoff equations under a variety of boundary controls involving boundary operators of order zero, one, and two; Schroedinger equations with Dirichlet control; first-order hyperbolic systems, etc., all on explicitly defined (optimal) spaces [LT3, Section 7]. Solution of the min-max problem implies solution of theH -robust stabilization problem with partial observation.The research of C. McMillan was partially supported by an IBM Graduate Student Fellowship and that of R. Triggiani was partially supported by the National Science Foundation under Grant NSF-DMS-8902811-01 and by the Air Force Office of Scientific Research under Grant AFOSR-87-0321.     

Synthesis, relaxometric and photophysical properties of a new pH-responsive MRI contrast agent: the effect of other ligating groups on dissociation of a p-nitrophenolic pendant arm

Two gadolinium(III) chelates, GdNP-DO3A (1-methlyene-(p-NitroPhenol)-1,4,7,10-tetraazacycloDOdecane-4,7,10-triAcetate) and GdNP-DO3AM (1-methlyene(p-NitroPhenol)-1,4,7,10-tetraazacycloDOdecane-4,7,10-triacetAMide), containing a single nitrophenolic pendant arm plus either three acetate or three amide pendant arms were synthesized and characterized. The properties of the gadolinium, terbium, and dysprosium complexes of these ligands were examined as a function of pH. The extent and mechanism of the changes in water relaxivity with pH of each gadolinium complex was found to differ substantially for the two complexes. The water relaxivity of Gd(NP-DO3A) increases from 4.1 mM(-1) s(-1) at pH 9 to 7.0 mM(-1) s(-1) at pH 5 as a result of acid-catalyzed dissociation of the nitrophenol from the lanthanide. The nitrophenol group in Gd(NP-DO3AM) does not dissociate from the metal center even at pH 5; therefore, the very modest increase in relaxivity in this complex must be ascribed to an increase in prototropic exchange rate of the bound water and/or phenolic protons.