New photoactivators for multiphoton excited three-dimensional submicron cross-linking of proteins: bovine serum albumin and type 1 collagen

We report the synthesis and optical characterization of two new photoactivators and demonstrate their use for multiphoton excited three-dimensional free-form fabrication with proteins. These reagents were developed with the goal of cross-linking Type 1 collagen. This cross-linking process produces structures on the micron and submicron size scales. A rose bengal diisopropyl amine derivative combines the classic photoactivator and co-initiator system into one molecule, reducing the reaction kinetics and increasing cross-linking efficiency. This derivative was successful at producing stable structures from collagen, whereas rose bengal alone was not effective. A benzophenone dimer connected by a flexible diamine tether was also synthesized. This activator has two photochemically reactive groups and is highly efficient in cross-linking bovine serum albumin and Type 1 collagen to form stable, robust structures. This approach is more flexible in terms of cross-linking a variety of proteins than by traditional benzophenone photochemistry. The photophysical properties vary greatly from that of benzophenone, with the appearance of a new, lower energy absorption band (lambda max approximately 370 nm in water) and broad, visible emission band (approximately 500 nm maximum). This absorption band is highly solvatochromic, suggesting it arises, at least in part, from a charge transfer interaction. Collagens are typically difficult to cross-link photochemically, and the results here suggest that these two new activators will be suitable for cross-linking other forms of collagen and additional proteins for biomedical applications such as the de novo assembly of biomimetic tissue scaffolds.     

Flat Spacetime Gravitation with a Preferred Foliation

Paralleling the formal derivation of general relativity as a flat spacetime theory, we introduce in addition a preferred temporal foliation. The physical interpretation of the formalism is considered in the context of 5-dimensional parametrized and 4-dimensional preferred frame contexts. In the former case, we suggest that our earlier proposal of unconcatenated parametrized physics requires that the dependence on be rather slow. In the 4-dimensional case, we consider and tentatively reject several areas of physics that might require a preferred foliation, but find a need for one in the process (flowing) theory of time. We then suggest why such a foliation might reasonably be unobservable.     

Evidence for chamber-dependent radical sources: Impact on kinetic computer models for air pollution

A series of NO_x–air irradiations, with trace amounts of propane and propene present to monitor OH radical concentrations, have been carried out in a 5800-L evacuable environmental chamber to investigate radical levels and sources during such irradiations. The data obtained show conclusively that unknown radical sources are present, and that photolysis of initial nitrous acid can be, at best, only a minor source of radicals after ～30–60 min of irradiation.     

C2O(Ã 3Πi↔-~X3Σ−: laser induced excitation and fluorescence spectra

Laser induced fluorescence of C₂O is observed following the 266 nm laser photodissociation Of C₃O₂. Excitation spectra of C₂O(óΠ_i?-~X³Σ^? are consistent with previous absorption studies of C₂O. A number of new transitions are identified and assigned. Fluorescence spectra have been recorded following single vibrational level laser excitation. Bands are assigned to ground state vibrational progressions. Values of 1967 and 1063 cm^?1 are found for υ₁″ and υ₃″ stretching vibrations in the X?³Σ ^? state. A subband structure in the fluorescence spectrum is observed and discussed.     

Excited state dynamics of C2O(A3Πi)

The fluorescence decay and bimolecular electronic quenching behavior of C₂O ($\text{A}$³Π_i) is reported. C₂O($\text{X}$³Σ^?) is produced by laser photolysis of C₃O₂ at 266 nm and is subsequently excited by a tunable flashlamp pumped dye laser. The fluorescence decay is highly nonexponential and dominated by both short (≈ 15 μs) and long (50–250 μs) decay components. The long-lived emission, itself, is nonexponential. The fluorescence decay is modeled as the sum of three exponential components. The short-lived emission is quenched by C₃O₂ at higher than the gas kinetic rate while the long-lived fluorescence is quenched much less efficiently. Fluorescence quenching measurements are also reported for collisions with Ar, N₂ and O₂.     

Kinetics of the reaction of oh radicals with a series of branched alkanes at 297 ± 2 K

Relative rate constants for the reaction of OH radicals with a series of branched alkanes have been determined at 297 ± 2 K, using methyl nitrite photolysis in air as a source of OH radicals. Using a rate constant for the reaction of OH radicals with n-butane of 2.58 × 10^?12 cm³/molecule · s, the rate constants obtained are (× 10¹² cm³/molecule · s): isobutane, 2.29 ± 0.06; 2-methylbutane, 3.97 ± 0.11; 2,2-dimethylbutane, 2.66 ± 0.08; 2-methylpentane, 5.68 ± 0.24; 3-methylpentane, 5.78 ± 0.11; 2,2,3-trimethylbutane, 4.21 ± 0.08; 2,4-dimethylpentane, 5.26 ± 0.11; methylcyclohexane, 10.6 ± 0.3; 2,2,3,3-tetramethylbutane, 1.06 ± 0.08; and 2,2,4-trimethylpentane, 3.66 ± 0.16. Rate constants for 2,2-dimethylbutane, 2,4-dimethylpentane, and methylclohexane have been determined for the first time, while those for the other branched alkanes are in generally good agreement with the literature data. Primary, secondary, and tertiary group rate constants at room temperature have been derived from these and previous data for alkanes and unstrained cycloalkanes, with the secondary and tertiary group rate constants depending in a systematic manner on the identity of the neighboring groups. The use of these group rate constants, together with a previous determination of the effect of ring strain energy on the OH radical rate constants for a series of cycloalkanes, allows the a priori estimation of OH radical rate constants for alkanes and cycloalkanes at room temperature.     

C2O(X3Σ−): absolute reaction rates measured by laser induced fluoresence

Absolute rate constants are reported for reactions of C₂O($\text{X}\text{?}$³Σ^?) under pseudo-first-order decay conditions. C₂O is generated by laser photodissociation of C₃O₂ at 266 nm, and detected by dye-laser induced fluorescence on the $\text{A}\text{?}$³Π_i-$\text{X}\text{?}$³Σ^? transition. Rate constants of (433 ± 12), (3.30 ± 0.12) and (1.12 ± 0.05) × 10^?13 cm³ molecule^?1 s^?1 are reported for reactions with NO, O₂ and isobutene. The NO value is approximate due to an apparent dark reaction between NO and C₃O₂. Upper limits of 1 × 10^?14 cm³ molecule^?1 s^?1 are reported for reactions with H₂, CO₂, C₃H₂ and C₂H₄. The C₂O + C₃O₂ reaction does not follow pseudo-first-order decay kinetics. Two explanations are proposed to explain this observation. Results are compared with previous relative rate measurements and are discussed in terms of their relevance to combustion chemistry.     

Rate constants for the reaction of O(3P) atoms with CH2 = CHF,CH2 = CHCl,and CH2 = CHBr at 298 ± 2°K

Absolute rate constants for the reaction of O(³P) atoms with CH₂ = CHF, CH₂ = CHCl, and CH₂ = CHBr have been obtained at 298 ± 2°K using a modulation phase shift technique. The rate constants (k₂ × 10^?8 l./mole · sec) obtained are: CH₂ = CHF (1.61 ± 0.20), CH₂ = CHCl (2.54 ± 0.26), and CH₂ = CHBr (2.45 ± 0.25). These rate constants are lower than those determined by discharge flow techniques, but that for CH₂ = CHF is in good agreement with relative rate measurements.     

Association of the T allele of an intronic single nucleotide polymorphism in the colony stimulating factor 1 receptor with Crohn's disease: a case-control study

BACKGROUND: Polymorphisms in several genes (NOD2, MDR1, SLC22A4) have been associated with susceptibility to Crohn's disease. Identification of the remaining Crohn's susceptibility genes is essential for the development of disease-specific targets for immunotherapy. Using gene expression analysis, we identified a differentially expressed gene on 5q33, the colony stimulating factor 1 receptor (CSF1R) gene, and hypothesized that it is a Crohn's susceptibility gene. The CSF1R gene is involved in monocyte to macrophage differentiation and in innate immunity. METHODS: Patients provided informed consent prior to entry into the study as approved by the Institutional Review Board at LSU Health Sciences Center. We performed forward and reverse sequencing of genomic DNA from 111 unrelated patients with Crohn's disease and 108 controls. We also stained paraffin-embedded, ileal and colonic tissue sections from patients with Crohn's disease and controls with a polyclonal antibody raised against the human CSF1R protein. RESULTS: A single nucleotide polymorphism (A2033T) near a Runx1 binding site in the eleventh intron of the colony stimulating factor 1 receptor was identified. The T allele of this single nucleotide polymorphism occurred in 27% of patients with Crohn's disease but in only 13% of controls (X2 = 6.74, p < 0.01, odds ratio (O.R.) = 2.49, 1.23 < O.R. < 5.01). Using immunohistochemistry, positive staining with a polyclonal antibody to CSF1R was observed in the superficial epithelium of ileal and colonic tissue sections. CONCLUSIONS: We conclude that the colony stimulating factor receptor 1 gene may be a susceptibility gene for Crohn's disease.