Effects of Intra-Base Pair Proton Transfer on Dissociation and Singlet Oxygenation of 9-Methyl-8-Oxoguanine−1-Methyl-Cytosine Base-Pair Radical Cations

8-Oxoguanosine is the most common oxidatively generated base damage and pairs with complementary cytidine within duplex DNA. The 8-oxoguanosine−cytidine lesion, if not recognized and removed, not only leads to G-to-T transversion mutations but renders the base pair being more vulnerable to the ionizing radiation and singlet oxygen (¹O₂) damage. Herein, reaction dynamics of a prototype Watson−Crick base pair [9MOG ⋅ 1MC]⋅⁺, consisting of 9-methyl-8-oxoguanine radical cation (9MOG⋅⁺) and 1-methylcystosine (1MC), was examined using mass spectrometry coupled with electrospray ionization. We first detected base-pair dissociation in collisions with the Xe gas, which provided insight into intra-base pair proton transfer of 9MOG⋅⁺ ⋅ 1MC [9MOG − H_N1]⋅ ⋅ [1MC+H_N3′]⁺ and subsequent non-statistical base-pair separation. We then measured the reaction of [9MOG ⋅ 1MC]⋅⁺ with ¹O₂, revealing the two most probable pathways, C5-O₂ addition and H_N7-abstraction at 9MOG. Reactions were entangled with the two forms of 9MOG radicals and base-pair structures as well as multi-configurations between open-shell radicals and ¹O₂ (that has a mixed singlet/triplet character). These were disentangled by utilizing approximately spin-projected density functional theory, coupled-cluster theory and multi-referential electronic structure modeling. The work delineated base-pair structural context effects and determined relative reactivity toward ¹O₂ as [9MOG − H]⋅>9MOG⋅⁺>[9MOG − H_N1]⋅ ⋅ [1MC+H_N3′]⁺≥9MOG⋅⁺ ⋅ 1MC.     

Negative electrospray ionization low-energy tandem mass spectrometry of hydroxylated fatty acids: a mechanistic study

Recently, we reported that by converting olefinic fatty acids to their saturated vicinally 1,2-di-hydroxylated derivatives, abundant ions indicative for hydroxyl group locations are produced by negative electrospray ionization low-energy tandem mass spectrometry, allowing the assignment of the olefinic site in the native fatty acid. In this report the mechanisms whereby the characteristic ions are produced are investigated. The mono-hydroxylated fatty acid, 12-hydroxyoctadecanoic acid, served as a model for the more complex 12,13-dihydroxyoctadecanoic acid, and fragmentation mechanisms accounting for the most abundant product ions generated from their deprotonated molecules are proposed. In general, three different mechanisms are proposed to operate in the formation of the observed product ions: (i) step-wise charge-remote homolytic cleavages, (ii) step-wise charge-proximate homolytic cleavages, and (iii) concerted charge-directed rearrangement reactions involving bond formation(s) and heterolytic cleavages. Support for the proposed mechanisms was achieved by investigating the deuterium- and oxygen-18-labeled isotopomers of both compounds.     

Laser mechanisms and processes in the p-GE far IR laser

Laser mechanisms in the p-Ge far IR laser are identified and models presented to make laser line assignments in the three laser spectral regions: (A) multiple frequencies non-tunable with E and B, (B) multiple frequencies tunable with B, and (CR) single cyclotron frequencies tunable with B. Brief reviews of the classical and quantum theories of the p-Ge laser are given to support and explain the laser models.     

Transient simulation of 2–3D stratified and intermittent two-phase flows. Part II: Applications

In this paper a new type of transient multidimensional two-fluid model has been applied to simulate intermittent or slug flow problems. Three different approaches to modelling interfacial friction, including an interfacial tracking scheme, have been investigated. The numerial method is based on an implicit finite difference scheme, solved directly in two steps applying a separate equation for the pressure. 2D predictions of Taylor bubble propagation in horizontal and inclined channels have been compared with experimental data and analytical solutions. The 2D model has also been applied to investigate a number of special phenomena in slug flow, including slug initiation, bubble turning in downflow and the bubble centring process at large liquid flow rates.     

Study of a new pervaporation membrane Part I. Preparation and characteristics of the new membrane

A new alcohol dehydration membrane, poly(vinyl alcohol)—chitosan blended composite membrane (PVA-CS) has been prepared. This membrane has high selectivity and promising permeability, especially in separating ethanol—water near the azeotropic region (J_t > 200 g/m² h, _w/e > 500, 70°C). The separating characteristics, which vary with feed composition, operating temperature and the surface structure of the membrane, are determined and the results agree well with the theoretical predictions.

The characteristics of mechanical strength, stability and resistance to water were also determined. The results show that they are considerably enhanced by blending and crosslinking, in comparison with PVA composite membranes.     

控制释放技术

综述药物控制释放的种类，机理，高分子材料在控制释放技术中的应用。     

Characterization of cellulose by SEC-MALLS

Norway spruce (Picea abies) cellulose samplesdissolved in lithium chloride/N,N-dimethyl-acetamide(LiCl/DMAc) covering a wide range of average molecular weights were analyzed bysize exclusion chromatography (SEC) and multi-angle laser light detection(MALLS). The molecular weight distribution of the samples was compared to themolecular weight distribution of cotton linters cellulose samples. To obtaincomplete dissolution of high-molecular-weight wood cellulose, previouslypublished procedures for dissolving cellulose in LiCl/DMAc were modified. SECseparation was performed using macroporous monodisperse polymer particles ascolumn matrix. The refractive index increment (dn/dc) forcellulose in 0.5% LiCl/DMAc was found to be 0.104. The radius of gyration,R_G, of cellulose in 0.5% LiCl/DMAc depended on the molecular weight,M, according to the relation R_G M^0.55. Celluloseprepared from sprucewood by the sulfite cooking process had a broad molecularweight distribution compared to cotton linters cellulose.     

Intracorneal Implantation of 3D Bioprinted Scaffolds Containing Mesenchymal Stromal Cells Using Femtosecond-Laser-Assisted Intrastromal Keratoplasty

Injury of the cornea is a complex biological process. Regeneration of the corneal stroma can be facilitated by the presence of mesenchymal stromal cells (MSCs) and application of tissue equivalents. A new tissue-engineering strategy for corneal stroma regeneration is presented using cellularized 3D bioprinted hydrogel constructs implanted into organ cultured porcine corneas using femtosecond laser-assisted intrastromal keratoplasty. The ex vivo cultured, MSC-loaded 3D bioprinted structures remain intact, support cell survival, and contain de novo synthesized extracellular matrix components and migrating cells throughout the observation period. At day 14 postimplantation, the cellularized tissue equivalents contain few or no cells, as demonstrated by optical coherence tomography imaging and immunofluorescent staining. This study successfully combines a laboratory-based method with modern, patient-care practice to produce a cell-laden tissue equivalent for corneal implantation. Optimal bioink composition and cellularization of tissue equivalents are essential in fine-tuning a method to promote the current technique as a future treatment modality.