Littérature scientifique sur le sujet « Formation of supramolecules »

While dipyrrin-boron complexes (BODIPYs) and their derivatives have attracted much attention, dipyrrin-based metal complexes recently appeared as a novel luminescent material. So far, dipyrrin-metal complexes have been regarded as non-luminescent or weakly luminescent. Interestingly, introduction of steric hindrance at the meso-position and the development of heteroleptic complexes with proper frontier orbital ordering are two recent strategies that have been developed to improve their luminescent ability. Compared with BODIPYs, one of the distinctive advantages of dipyrrin-metal complexes is that they can form a series of self-assembled supramolecules and polymer assemblies via facile coordination reactions. In recent times, several supramolecular, coordination polymers and Metal-Organic Frameworks (MOFs) have been developed, [Formula: see text] by spontaneous coordination reactions between dipyrrin ligands and metal ions. As a novel luminescent material, dipyrrin-metal complexes have been applied in many fields. This review article summarizes recent developments in dipyrrin-metal complexes from the viewpoint of the improvement of luminescent ability, the formation of supramolecular and coordination polymers and their potential applications.

Enzymatic polymerization has been noted as a powerful method to precisely synthesize polymers with complicated structures, such as polysaccharides, which are not commonly prepared by conventional polymerization. Phosphorylase is one of the enzymes which have been used to practically synthesize well-defined polysaccharides. The phosphorylase-catalyzed enzymatic polymerization is conducted using α-d-glucose 1-phosphate as a monomer, and maltooligosaccharide as a primer, respectively, to obtain amylose. Amylose is known to form supramolecules owing to its helical conformation, that is, inclusion complex and double helix, in which the formation is depended on whether a guest molecule is present or not. In this paper, we would like to report the preparation of amylose-carboxymethyl cellulose (CMC) conjugated supramolecular networks, by the phosphorylase-catalyzed enzymatic polymerization, using maltoheptaose primer-grafted CMC. When the enzymatic polymerization was carried out using the graft copolymer, either in the presence or in the absence of a guest polymer poly (ε-caprolactone) (PCL), the enzymatically elongated amylose chains from the primers on the CMC main-chain formed double helixes or inclusion complexes, depending on the amounts of PCL, which acted as cross-linking points for the construction of network structures. Accordingly, the reaction mixtures totally turned into hydrogels, regardless of the structures of supramolecular cross-linking points.

Supramolecular chemistry covers intermolecular interactions where non-covalent bonds are involved, and many of them are based on host-guest interactions. Cyclodextrins (CDs) are cyclic oligosaccharides consisting of 6-, 7- or 8-glucose units, which are called alpha-, beta- or gamma-CDs, respectively. They have hydrophobic interior and hydrophilic exterior, and are widely being used as hosts for various organic molecules. The formation of CD inclusion complexes with a variety of dyes has continuously drawn our interests, since CDs are readily available and have ability to include dye molecules altering their properties. The present thesis covers the study of inclusion complexes of CDs and chromophore dyes, largely in two ways; rotaxane and pseudorotaxane. The stable rotaxane structure is achieved with the synthesis of dye rotaxane. The introduction of CD ring around azo chromophore provides a simple way to improve the solubility and stability of azo dye. We have shown that by incorporating proper compounds as a coupler, azo dye rotaxanes can be used as pH indicators and metal ion sensors. We have described the synthesis of novel acetylene dye rotaxane using the Pd-catalyzed reaction of Heck-Cassar-Sonogashira-Hagihara type. Its fluorescence properties in the solid state as well as in solutions are examined and compared with those of free dye. Free dye, which has tetra-carboxylic groups, is found to be highly sensitive to various metal ions, exhibiting high Stern-Volmer constants, K(SV). On the contrary, acetylene dye rotaxane exhibits much less quenching against various quenchers. The appearance of fluorescent anisotropic structure has been observed by the formation of inclusion complex between acetylene dye and gamma-CD. Its structural nature is studied by various techniques, including fluorescence, fluorescence anisotropy, wide angle X-ray scattering (WAXD) and differential scanning calorimetry (DSC) measurements. Methyl orange, an acid azo dye, forms a dimeric inclusion complex with gamma-CD, resulting in the formation stable anisotropic aggregates. Several other azo dyes are found to form anisotropic supramolecule in the presence of gamma-CD, and their structural characteristic has been discussed in terms of the number and position of solubilizing groups.

The spontaneous formation of supramolecular assemblies has been viewed as a potential route to the creation of functional nano-scale architectures for a number applications in electronics. In this thesis a number of assemblies formed from molecular constituents deposited from the solution phase have been studied. The structures formed by two carboxylic acid derivatives on the highly oriented pyrolytic graphite (HOPG) surface from nonanoic acid solutions are presented. Quaterphenyl-tetracarboxylic acid (QPTC) molecules are observed to form a supramolecular network where all the constituents lay parallel to one another on the surface. The network is stabilised by four carboxylic acid dimer bonds per molecule in addition to admolecule-substrate interactions. Terphenyl-tetracarboxylic acid (TPTC) molecules form a much more complex structure with individuals orientating themselves in one of three directions to form a network with hexagonal symmetry but no translational order. To characterise such an unusual supramolecular morphology we introduce a rhombus tiling representation of the network where each molecule is schematically replaced with a lozenge rhombus producing a tiling. Such tilings have been studied previously in the literature and utilising this we are able to determine that the morphology is stabilised by entropic contributions to the free energy. In addition to this we present the tip-induced manipulation of the TPTC supramolecular network. The manipulation is performed by imaging the structure within a specific voltage bias range resulting the TPTC molecules reordering into a close packed structure. Returning the voltage to that conventional used for imaging causes the network to relax back into the open structure although with a different morphology. We then discuss the changes induced in these supramolecular networks when additional molecular species are introduced to the system. First, coronene and perylene are separately codeposited with QPTC resulting in the formation of a hexagonally ordered network with coronene or perylene located at the vertices of six QPTC molecules. This new structure is observed to form even when QPTC is deposited first. Second, the adsorption of coronene into the porous TPTC network is presented. When the TPTC network forms before the introduction of coronene we note little effect on the network morphology. However, when the molecules are mixed in the solution phase and deposited simultaneously we observe the non-uniform adsorption of coronene into the TPTC structure. At higher coronene concentrations we note the network forms with a different morphology shifted towards a more ordered state suggesting that when the molecules are deposited sequentially the system is kinetically trapped in the originally formed structure. We then present a series of studies of molecular adsorption on the Au (111) surface. First, hexaazatrinaphthylene (HATNA) molecules are observed to form stable supramolecular structures when deposited from ethanol solutions. A core hydrogen bonding junction is identified. The network switches between two domain orientations and we identify a linear defect where the two domains meet. Second, we report the adsorption of Tri( 4-bromophenyl) benzene (TBPB) on the Au (111) surface. TBPB forms three different structures at room temperature. When samples are heated during the deposition stage we observe the covalent coupling of pairs of molecules to form dimers. This reaction is confirmed by ToFSIMS experiments. The substrate is confirmed to play a significant role in the coupling process as subsequent experiments on HOPG failed to yield dimer formation. Finally we demonstrate the potential of a UHV-prepared sample by templating the adsorption of adamantanethiols. Finally, we demonstrate the adsorption of a solubilised derivative of perylene tetracarboxylic dianhydride (PTCDA). PTCDA molecules have poor solubility in most solvents commonly used for liquid deposition. The addition of alkane chains attached to the sides of the perylene core promotes the solubility of the molecule in these solvents whilst leaving the anhydride functionality intact. Deposition is performed from 1-phenyloctance solutions on HOPG. The molecules form an ordered structure characterised by a single molecule unit cell. The results presented in this thesis show that the understanding of supramolecular networks has progressed to the point where changes in the morphology can be induced via a variety of processes.

The chemical and physical properties of organic molecular crystals depend on both the molecular and crystal structure. The systematic approach to understanding and controlling crystal structure lies in the field of "crystal engineering". One strategy to emerge within crystal engineering has been the utilisation of specific interactions or couplings / synthons to predictably build supramolecular arrays such as tapes, ribbons or sheets. These arrays form a subset of the crystal structure. While many couplings take the form of cyclic motifs in which component interactions are of comparable strength, a cyclic coupling consisting of an O-- H^...N and a C-H^...O interaction was noted as having a potential use in designing supramolecular arrays. This type of strong / weak coupling is possible upon the interaction of an N-heterocycle with a carboxyl group. The following research describes the co-crystallisation of various N-heterocyclic bases with a number of olefinic and aliphatic dicarboxylic acids. The crystal structures of various complexes of phenazine, 1,10-phenanthroline and quinoxaline were solved from single-crystal X-ray diffraction data and are discussed. Two distinct strong / weak couplings were identified within the three sets of co-crystals. A comparison of the relative stabilities of the two couplings was made using the quinoxaline system. Supramolecular tapes were observed in all of the phenazine co-crystals and in three of the four quinoxaline co-crystals. (The stoichiometry of the phenazine co-crystals may be related to the position of the carboxyl groups on the participating acid.) The packing of the tapes is discussed with particular reference to tape topography and inter-tape C-H^...O interactions. Proton transfer occurred in four of the five co-crystals of 1,10-phenanthroline. Co-crystals were prepared via two methods: by growth from a solution and by grinding of a physical mixture of the starting components. Solid-state grinding was found to be a viable method for the preparation of co-crystals. Complexes of 1,10-phenanthroline prepared via the two routes were analysed using solid-state ¹³C MAS NMR and the effects of protonation on certain carbon resonances is discussed.

Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: A theoretical and experimental study was performed in order to identify factors that influence the propensity of compounds containing anionic functional groups that are commonly found on pharmaceutical drug compounds to form hydrates. A Cambridge Structural Database (CSD) survey was initially undertaken to determine the propensity of different pharmaceutically acceptable anions to form hydrates. The results showed that hydrate formation will take place more regularly when the polarity of the functional group increases. Furthermore, if the charge distribution is very concentrated over the polar groups, hydrate formation will occur more readily. This observation was further investigated by performing a series of potential energy surface (PES) scans for the hydrogen bond (H-bond) in the structure of N-(aminoiminomethyl)-N-methylglycine monohydrate (creatine monohydrate) with various Density Functional Theory (DFT) and Wave Functional Theory (WFT) methods. WFT is often also referred to as ab initio, which refers to the construction of the wave function from first principles when this theory is applied. The scans revealed that several strong and directional H-bonds with different geometrical parameters between the carboxylate group and the water molecule are possible, which suggests that the H-bond plays an important role in driving the formation of pharmaceutical hydrates. A total of 44 hydrate structures were identified that have pharmaceutically acceptable functional groups. Optimisations in the gas phase and in an implicit solvent polarisable continuum solvent model with a variety of solvents showed that there is a significant dependence of the H-bond interaction energy on the anionic group as well as the steric density of surrounding substituents. It was found that the M06-2X method utilising the 6-311++G(d,p) basis set outperformed the other methods that were tested when compared to optimisations performed with the benchmark MP2/aug-cc-pVTZ level of theory. Furthermore, the strength of the H-bond was measured in the 44 experimentally determined structures by using a total of five generalized gradient approximation (GGA) methods, of which two methods contained the DFT-D3 correction. The results of these DFT methods were subsequently compared to results obtained at the benchmark MP2/aug-cc-pVTZ level of theory. The M06-2X method was identified as the most economical method to calculate H-bond energies. It was also found that the H-bond interaction energy shows a substantial dependence on the electrostatic environment. This was observed by a significant decrease in H-bond strength as the relative permittivity of the solvent increases. The effect of steric density on the H-bond interaction energy was investigated by performing hydrogen bond propensity calculations. These values were then compared to the interaction energies of each structure and the results showed that the presence of large bulky substituents can lead to an increase in bond energy by forcing the anionic functional group closer to the water molecule. Contrastingly, the bulky group can also push the anionic group away from the water molecule and result in a decrease in bond energy. Approximate values for the amount of stabilisation offered to the H-bonding system by the surrounding crystalline environment were calculated by optimising the H-bond geometrical parameters of selected compounds with a combination of the M06-2X and MP2 methods utilising the 6-311++G(d,p) basis set. The H-bond interaction energies were then calculated at the M06-2X/6-311++G(d,p) level of theory and compared to the H-bond interaction energies in geometries that have been fully optimised. After these energies were compared and the crystal packing of each structure was investigated, it was found that the packing of some structures within the crystalline environment limits the number of H-bonds that can be formed between the water and the compound of interest. Full optimisation calculations result in structures with cooperative stabilisation, such that more than one H-bond is found between the two fragments. The effect of substituents on H-bond interaction energy was investigated by the addition of six electron-donating and electron-withdrawing groups on four aromatic compounds with different anionic functional groups, namely carboxylate, nitrogen dioxide, sulfonate and phosphonate. It should also be mentioned that the nitrogen dioxide is not an anionic functional group, but it was included as it is a neutral radical that often forms hydrogen bonds. A total of 80 structures were optimised with a combination of the M06-2X and MP2 methods utilising the 6-311++G(d,p) basis set. This was followed by counterpoise corrected single point calculations at the M06-2X/6-311++G(d,p) level of theory. The results showed that the H-bond interaction energy bears no relationship to the inductive strength or the inductive ability of the substituents, but rather the ability of these substituents to rotate the anionic functional group and allow cooperative stabilisation of the H-bond. Furthermore, AIM analysis was performed for the substituted H-bonded aromatic structure. The results showed that electron-donating groups that are placed at the para position yield stronger H-bonds, which is once again accompanied by cooperative stabilisation. Electron-withdrawing groups with sufficient inductive effects can result in a weaker H-bond when placed at the meta position. The effect of water activity (aw) on the hydrate crystal formation was investigated experimentally by performing a series of crystallisations in various solvent mixtures. These mixtures consisted of water mixed with acetone, ethanol and ethyl acetate. A total of three organic acids were used in crystal formation, namely pyridine-4-carboxylic acid (isonicotinic acid), N-amino-iminomethyl-N-methylglycine (creatine) and benzene-1,3,5-tricarboxylic acid. It was found that water activity affects the formation of the hydrate as well as the anhydrous product. Additionally, nucleation and super saturation plays a large role in crystal formation and can serve as an effective technique when the formation of crystals of an appropriate shape and size is required for further analysis.
AFRIKAANSE OPSOMMING: 'n Teoretiese en eksperimentele studie was uitgevoer om faktore te identifiseer wat die geneigdheid van verbindings met anioniese funksionele groepe wat algemeen gevind word op farmaseutiese dwelm verbindings om die hidraat produk te vorm, affekteer. 'n Opname van strukture in die Cambridge Strukturele Databasis (CSD) is onderneem om die geneigdheid van verskillende farmaseutiese aanvaarbare anione om hidrate te vorm te bepaal. Die resultate het getoon dat hidraatvorming meer gereeld plaasvind indien die polariteit van die funksionele groepe toeneem. Verder is daar ook opgemerk dat 'n gekonsentreerde ladingsverspreiding op die polêre groepe ook tot 'n toename in hidraat vorming sal lei. Hierdie waarneming is verder ondersoek deur 'n reeks potensiële energie oppervlak (PES) skanderings van die waterstof binding (H-binding) vir die struktuur van N-amino-iminometiel-N-metielglisien monohidraat (kreatien monohidraat) met verskeie Digtheids-Funksionele Teorie (DFT) en Golffunksie Teorie (WFT) metodes uit te voer. Die skanderings het getoon dat verskeie sterk, gerigte H-bindings met verskillende geometriese parameters tussen die karboksilaatgroep en die watermolekule kan vorm. Hierdie bevindinge lê klem op die belangrike rol wat H-bindings in die vorming van farmaseutiese koolhidrate speel. 'n Totaal van 44 hidraat strukture met farmaseutiese aanvaarbare funksionele groepe was geïdentifiseer. Optimaliserings is in die gas fase asook in 'n implisiete kontinuum polariseerbare oplosmiddel model met 'n verskeidenheid oplosmiddels uitgevoer. Die resultate het 'n beduidende afhanklikheid van die H-binding interaksie-energie op die anioniese groep asook die steriese afkskerming van omringende groepe getoon. Daar is bepaal dat die M06-2X metode wat saam met die 6-311++G(d,p) basisstel die mees akkuraatste resultate gelewer het in vergelyking met die ander DFT metodes asook die MP2/aug-cc-pVTZ maatstaf. Die H-binding se sterkte is vir hierdie strukture bereken deur vyf GGA metodes te gebruik, waarvan twee metodes van die DFT-D3 korreksie gebruik maak. Die resultate van die berekeninge met hierdie DFT metodes is daarna vergelyk met resultate verkry met die MP2/aug-cc-pVTZ maatstaf. Daar is gevolglik bepaal dat die M06-2X metode die mees ekonomiese metode is om H-binding energië te bereken. Die H-binding interaksie energie toon 'n aansienlike afhanklikheid op die diëlektriese konstante van die oplosmiddel aan. Hierdie waarneming is op grond van 'n beduidende afname in die H-binding interaksie-energie indien die relatiewe permittiwiteit van die oplosmiddel verhoog word gemaak. Die effek van steriese digtheid is ondersoek deur waterstofbindinggeneigdheid waardes te bereken. Hierdie waardes is met die interaksie-energië van elke struktuur vergelyk. Die resultate dui daarop dat steries digte groepe tot 'n toename in interaksie energie kan lei wanneer die anioniese funksionele groep nader aan die water molekule gestoot word. Verder is dit ook moontlik vir hierdie steries digte groepe om die anioniese groep weg van die water molekule te stoot en gevolglik 'n afname in interaksie energie te veroorsaak. Benaderde waardes vir die hoeveelheid stabilisering wat die omringende kristallyne omgewing aan die H-binding bied is bereken deur die H-binding geometriese parameters van geselekteerde verbindings met die M06-2X en MP2 metodes en die 6-311++G (d,p) basisstel te optimaliseer. Die H-binding interaksie-energië is gevolglik by die M06-2X/6-311++G(d,p) vlak van teorie bereken en met die H-binding energië in strukture wat volledige optimaliseer is vergelyk. Nadat hierdie waardes vergelyk is, is daar gevind dat die pakking van strukture in the kristallyne omgewing verhoed dat sekere H-bindings tussen die water molekule en die verbinding van belang kan vorm. Strukture wat volledig optimaliseer is, lei tot strukture wat in staat is om koöperatiewe stabilisering te ondergaan. Koöperatiewe stabilisering word gekenmerk deur die vorming van meer as een H-binding tussen twee fragmente. Die effek van substituente op die H-binding interaksie energie is ondersoek deur die bevoeging van ses elektrondonor- en elektronontrekkendegroepe op vier aromatiese verbindings, naamlike die karboksilaatgroep , stikstofdioksied , sulfonaat en fosfonaat. Dit moet ook genoem word dat stikstofdioksied nie 'n anioniese funksionele groep is nie, maar dit was wel ingesluit omdat dit ‘n neutrale radikaal groep is wat dikwels waterstofbindings vorm. 'n Totaal van 80 strukture optimiserings was uitgevoer met 'n kombinasie van die M06-2X en MP2 metodes wat gebruik maak van die 6-311++G(d,p) basisstel. Dit is gevolg deur interaksie-energie berekeninge op die M06-2X/6-311++G(d,p) vlak van teorie. Die resultate het getoon dat daar geen verband tussen die induktiewe vermoë van die substituente en die sterkte van die H-binding is nie, dit is eerder die vermoë van hierdie substituente om die anioniese funksionele groep te laat roteer wat toelaat dat koöperatiewe stabilisering van die H-binding kan geskied. Die AIM analise is op 'n gesubstitueerde H-binding struktuur toegepas. Die resultate het getoon dat elektrondonorgroepe wat by die para posisie geplaas word tot sterker H-bindings sal lei, wat weereens met koöperatiewe stabilisering vergesel word. Elektrononttrekkendegroepe met sterk induktiewe effekte kan tot 'n swakker H-binding lei indien hulle by die meta posisie geplaas word. Die effek van water aktiwiteit (𝑎w) op hidraatkristalvorming is deur die uitvoering van 'n reeks kristallisasies in verskeie oplosmiddelmengsels ondersoek. Hierdie oplosmiddel mengsels bestaan uit water met asetoon, etanol of etielasetaat gemeng. Kristallisasies is vir drie organiese sure, naamlik piridien-4-karboksielsuur, N-amino-iminometiel-N-metielglisien monohidraat en 1,3,5-benseen tri-karboksielsuur uitgevoer. Daar is gevind dat water aktiwiteit 'n invloed op die vorming van die hidraat en watervrye produkte kan hê. Daarbenewens, speel water aktiwiteit 'n belangrike rol in die nukleasie fase van kristalvorming en kan as 'n effektiewe tegniek dien om kristalle van 'n toepaslike vorm en grootte vir verdere analise te verkry.

Abstract The traditional chemical cross-linking method is based on the formation of covalent bonds between molecules to connect three-dimensional networks to enhance the strength of hydrogels. Although this method can significantly improve the mechanical properties, it also has many problems, such as irreversibility and fatigue. Therefore, the design and preparation of supramolecular hydrogels with high mechanical properties and good temperature resistance have very important research significance and practical value. This paper prepared a supramolecular gel with both temperature resistance and mechanical properties through hydrophobic association and hydrogen bonding, and evaluated its thermal stability, rheology, temperature resistance and pressure plugging ability. The results showed that the supramolecular gel had excellent thermal stability, and there was strong physical entanglement between its three-dimensional network structures, which made it difficult to be destroyed by increasing temperature. The excellent rheological properties of supramolecular gels enable them to maintain good viscoelastic changes in the linear viscoelastic region within the strain range of 0.1-30%. When the strain was greater than 30%, the supramolecular gel began to undergo different degrees of sol-gel phase transition, which showed that the energy storage modulus of supramolecular gel decreased. In addition, the energy storage modulus of supramolecular gel was always greater than the loss modulus in the whole frequency scanning range, and there was no intersection between the two gel and the gel always showed high elasticity. Meanwhile, the supramolecular gel still had good structure and strength after high temperature aging. Its tensile and compressive properties did not change significantly, but the color of the gel surface changed slightly, which could maintain good structural stability under high temperature environment. Supramolecular gel particles could be used as plugging materials for drilling fluid, and had excellent plugging ability of formation fractures and pores. The plugging ability of 1mm aperture plate model was up to 6.3MPa, and the plugging ability of 1mm seam width was up to 4.9MPa. Therefore, the development and application of supramolecular gel plays an important supporting role in drilling fluid plugging.

The self-assembly of supramolecular complexes between DNA and lipophilic vitamins, e.g. vitamin D group was examined, in the absence and presence of different cations, to the first time. A novel method for preparing DNA-lipophilic vitamins nanostructured complexes in the existence of divalent cations is introduced. The nanostructure of the supramolecular complexes ranged from beads-on-strings to compact globules and liquid crystalline forms depending on the vitamin nature, cations concentration and incubation time. A nucleation mechanism and flower-like aggregates are proposed as an initial state for complex formation. The biomedical applications of the functional nanostructured supramolecular complexes will be discussed in details.

Laser light scattering (LLS), small angle x-ray scattering (SAXS) and small angle neutron scattering (SANS) are complementary techniques.1 Together they become unmatched among the physical methods which can investigate the structure and dynamics of polymeric materials over a large range of length and time scales. The unique features of LLS are its ability to determine not only molecular weight, size and internal motions of polymers in solution or of colloids in suspension, but also the size distribution. The applications of LLS to polymer physics and colloid science have been extensive and noteworthy, especially in particle size analysis. In this lecture, three unique examples on (1) Teflon solution characterization,2 (2) coil-to-globule transition3, and (3) supramolecular formation of block copolymers in selective solvents4 are presented.

Abstract Mucus is a complex fluid that maintains moisture and simultaneously acts as a barrier and facilitates transport of select materials between the body and adjacent fluids. While mucus is comprised primarily of water, it is highly heterogeneous containing the biopolymer mucin along with lipids, salts, DNA, proteins, and cells. Complex mechanisms control the reversible network formation observed in mucus and mucin solutions. Some isolated relationships between biopolymer network structure, pH and ionic strength, and rheology have been identified; however, a complete understanding of the interplay in these mechanisms is lacking. In this effort, rheology of native mucus and mucin solutions was examined as a function of pH and salt concentration. Bulk rheology of native and artificial lung mucus confirmed that native mucus displays a solid-like behavior at low strain values. Mucus displays this solid-like gel behavior at pH values ca. 4 and below, and displays solution behavior at higher pH values. Ion concentration also plays an important role with divalent cations (Ca2+) reducing the viscosity of gelled mucin and increasing the viscosity of solution-state mucin. In addition to rheological characterization, mucin-mucin and mucin-solute interactions and resultant changes in microstructure were also studied. Morphological and chemical changes at the nano-scale were correlated to the micro-structural changes observed with rheology. Dynamic light scattering showed mucin polymer particle size heterogeneity as well as a significant increase in particle size at pH values ca. 4 and below — where the solutions display a gel behavior. Using zeta potential a decrease in dispersive forces was observed that allows for polymer-polymer interaction and particle aggregation at low pH values. Atomic force micrography showed spheroid-like aggregates between adjacent mucin particles under acidic conditions. The ability to understand and control the reversible association of network structures in polymer and biopolymer systems, such as mucin, through supramolecular interactions has fundamental impacts in the field of polymer science and engineering. There is also significant potential to advance applications involving novel hydrogel materials, such as disease treatments and drug delivery.

In mature fields, low oil production, increased gas production and water fractional flow of low pressure reservoir combined with the mobility ratio between the gas and oil feed contacts the w/o induced by the oil extraction process are accentuated in naturally fractured reservoirs (NFR) -. It is common N2 injection for pressure maintenance and decline of oil production; however N2 causes channeling towards producing wells. In various fields - NFR, closure of oil production by this mechanism loss value make unprofitable oil production and surface facilities for handling demanding high volume gas and / or water or gas production out of specification. In volumes estimated residual oil trapped in areas invaded by the gas cap and in areas of lower conductivity can be recovered if it has clearly identified enhanced recovery processes. Previous efforts to this work results showed potential benefits in terms of increased oil production and the significant reduction of Gas-Oil Ratio (GOR) and the technical and economic feasibility of using this type of process with surfactants developed specifically for the conditions of this area The technology tested and evaluated under methodological process is based on new supramolecular complexes wettability modifier, corrosion inhibitor and able to generate stable foams under high pressure, temperature and salinity, which penetrate and invade the channels of high conductivity formation cause decreased flow of gas by reducing gas mobility. The product in the liquid phase diffuses into the channels of lower conductivity which cannot penetrate the foam, and by spontaneous imbibition mechanism resulting from the change of wettability of the rock surface and reducing interfacial tension and favors an increase the oil recovery factor in naturally fractured reservoirs. The application of a methodological process allowed the parameters measurement and evaluation of test results, visualizing future opportunities for the new chemicals. This project was approved after evaluation from a process of allocation of federal funds. With the purpose of defining the further steps in the search for the chemicals stability and risk mitigation stages of industrial upgrading for the complexity the NFR, the following discussion is presented. In order to accelerate the knowledge of new technologies and its deployment on the field, PEMEX has diversified the efforts, to achieve the principal goals regarding new technologies. This will provide greater ability to assess best practices and technologies. To evaluate the efforts of companies a performance assessment model was designed and apply from 2008, which takes into account the integral complexity of each technology to attend the specific challenges from an Asset and to be fair in comparing the results obtained for the particular design of the test. The aim of this paper is to describe the results and the methodology used for developing the performance evaluation and identifying the new opportunities in the state of the art of these tests.

In this project, we studied the photosynthetic apparatus during dehydration and rehydration of the homoiochlorophyllous resurrection plant Craterostigmapumilum (retains most of the photosynthetic components during desiccation). Resurrection plants have the remarkable capability to withstand desiccation, being able to revive after prolonged severe water deficit in a few days upon rehydration. Homoiochlorophyllous resurrection plants are very efficient in protecting the photosynthetic machinery against damage by reactive oxygen production under drought. The main purpose of this BARD project was to unravel these largely unknown protection strategies for C. pumilum. In detail, the specific objectives were: (1) To determine the distribution and local organization of photosynthetic protein complexes and formation of inverted hexagonal phases within the thylakoid membranes at different dehydration/rehydration states. (2) To determine the 3D structure and characterize the geometry, topology, and mechanics of the thylakoid network at the different states. (3) Generation of molecular models for thylakoids at the different states and study the implications for diffusion within the thylakoid lumen. (4) Characterization of inter-system electron transport, quantum efficiencies, photosystem antenna sizes and distribution, NPQ, and photoinhibition at different hydration states. (5) Measuring the partition of photosynthetic reducing equivalents between the Calvin cycle, photorespiration, and the water-water cycle. At the beginning of the project, we decided to use C. pumilum instead of C. wilmsii because the former species was available from our collaborator Dr. Farrant. In addition to the original two dehydration states (40 relative water content=RWC and 5% RWC), we characterized a third state (15-20%) because some interesting changes occurs at this RWC. Furthermore, it was not possible to detect D1 protein levels by Western blot analysis because antibodies against other higher plants failed to detect D1 in C. pumilum. We developed growth conditions that allow reproducible generation of different dehydration and rehydration states for C. pumilum. Furthermore, advanced spectroscopy and microscopy for C. pumilum were established to obtain a detailed picture of structural and functional changes of the photosynthetic apparatus in different hydrated states. Main findings of our study are: 1. Anthocyan accumulation during desiccation alleviates the light pressure within the leaves (Fig. 1). 2. During desiccation, stomatal closure leads to drastic reductions in CO2 fixation and photorespiration. We could not identify alternative electron sinks as a solution to reduce ROS production. 3. On the supramolecular level, semicrystalline protein arrays were identified in thylakoid membranes in the desiccated state (see Fig. 3). On the electron transport level, a specific series of shut downs occur (summarized in Fig. 2). The main events include: Early shutdown of the ATPase activity, cessation of electron transport between cyt. bf complex and PSI (can reduce ROS formation at PSI); at higher dehydration levels uncoupling of LHCII from PSII and cessation of electron flow from PSII accompanied by crystal formation. The later could severe as a swift PSII reservoir during rehydration. The specific order of events in the course of dehydration and rehydration discovered in this project is indicative for regulated structural transitions specifically realized in resurrection plants. This detailed knowledge can serve as an interesting starting point for rationale genetic engineering of drought-tolerant crops.