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Η μελέτη αυτή αφορά το σχεδιασμό των μιγμάτων πρωτεΐνης/πολυηλεκτρολύτη και τις αλληλεπιδράσεις τους σε φυσιολογικές συνθήκες. Η παρακάτω έρευνα περιλαμβάνει σύμπλοκα αλβουμίνης ορού βοοειδούς (BSA) με ένα σύνολο κατιονικών ομοπολυμερών και συμπολυμερών πολύ (3-μεθακρυλαμιδο-προπυλο- τριμεθυλαμμωνιο-χλωριδιο) -co- (Ν, Ν-διμεθυλακρυλαμίδιο), με διαφορετικό μοριακό βάρος και σύσταση σε ομάδες πολυ (Ν, Ν- διμεθυλακρυλαμιδίου) (PDMAM). Μετρήσεις UV-VIS φασματομετρίας, η σκέδαση φωτός και ζ-δυναμικό συμμετείχαν στο χαρακτηρισμό των συσσωματωμάτων ως μία συνάρτηση της αναλογίας φορτίου r +/- , του pΗ και της ιοντικής ισχύος. Τα αποτελέσματα έδειξαν το σχηματισμό αντίθετων φορτισμένων συμπλόκων, σε pΗ υψηλότερο από 4.9, το ισοηλεκτρικό σημείο της BSA. Τέτοια σωματίδια βρέθηκαν να εξαρτώνται από την πυκνότητα φορτίου της επιφάνειας της πρωτεΐνης η οποία επηρεάζει σημαντικά τις ηλεκτροστατικές αλληλεπιδράσεις. Ως αποτέλεσμα, για ένα ομοπολυμερές PMAPTAC ο σχηματισμός αδιάλυτων συμπλοκών ευνοείται για υψηλές τιμές pΗ, όπου η πυκνότητα επιφανειακού φορτίου της πρωτεΐνης είναι μέγιστη. Αντίθετα, αύξηση της ιοντικής ισχύος οδηγεί σε καταστολή των απώσεων μακράς εμβέλειας μεταξύ των αρνητικά φορτισμένων περιοχών του πολυηλεκτρολύτη και της πρωτεΐνης, εξαιτίας τοπικών ηλεκτροστατικών επιδράσεων. Οι διαφορές στο σχηματισμό συμπλόκου επιβεβαιώθηκαν με σύγκριση δύο PMAPTAC ομοπολυμερών με διαφορετικά μοριακά βάρη σε σταθερό pΗ. Αυτά τα συσσωματώματα έδειξαν διαφορές στο μέγεθος και τις επιφανειακές ιδιότητες οδηγούμενες από την πυκνότητα φορτίου του πολυηλεκτρολύτη. Έτσι, τα μεγαλύτερα σωματίδια ελήφθησαν από το πολυκατιόν με υψηλότερο μοριακό βάρος σε pΗ 7,40. Ακόμα, ο ρυθμός κατανάλωσης της BSA για το σχηματισμό συμπλόκου με τον πολυηλεκτρολύτη ήταν παρόμοιος για όλες τις περιπτώσεις διαφορετικού pH δίνοντας έτσι το γεγονός ότι η καταβύθιση της BSA είναι ανεξάρτητη του pH. Η προσθήκη ουδέτερα υδρόφιλου PDMAM επεκτείνει το πιθανό μηχανισμό συμπλοκοποίησης. Με τη σύγκριση μιας σειράς από συμπολυμερή που φέρουν διαφορετικό αριθμό των υδρόφιλων ομάδων DMAM, μόνο διαλυτά σύμπλοκα πολυηλεκτρολύτη / πρωτεΐνης σχηματίζονται με υδροδυναμικά μεγέθη <50 nm. Η συμπεριφορά αυτή έχει αποδοθεί στην παρουσία των υδρόφιλων μονάδων DMAM που απλά δρα ως προστατευτικό εξωτερικό κέλυφος των συσσωματωμάτων εμποδίζοντας περαιτέρω συσσωμάτωση. Συνεπώς, από τα σύμπλοκα που σχηματίζονται από το συμπολυμερές με την διαφορετική περιεκτικότητα DMAM, ισχυρότερη προτίμηση ένωσης με την πρωτεΐνη έδειξε το συμπολυμερές με τη χαμηλότερη περιεκτικότητα DMAM. Αυτό δείχνει τη σημασία των υδρόφιλων ομάδων οι οποίες παρεμποδίζουν στερεοχημικά την πρόσβαση ή έκθεση των ιόντων στην επιφάνεια του συμπλόκου. Ακόμα, το υδρόφιλο εξωτερικό κέλυφος είναι είτε μικρότερο, είτε λιγότερο πυκνό, γεγονός που επιτρέπει την αναδιάταξη των σωματιδίων έτσι ώστε περισσότερα φορτία να είναι παρών στην επιφάνεια του 4 συσσωματώματος που μπορεί περαιτέρω να αλληλεπιδρούν με το κατιονικό πολυηλεκτρολύτη. Έτσι, το σύστημα που παρουσιάζεται εδώ δίνει μία εις βάθος μελέτη των πιθανών μηχανισμών των αλληλεπιδράσεων πολυηλεκτρολύτη με πρωτεΐνες. Επιπλέον, ο σχηματισμός συμπλοκών μικρής κλίμακας σταθερών σε υδατικό διάλυμα επιτεύχθηκε με ρύθμιση παραμέτρων, όπως το μοριακό βάρος, η αναλογία φορτίου και της ισορροπίας υδρόφιλου / υδρόφοβου. Επιπρόσθετα, τα συστήματα ήταν σε συμφωνία με περιβαλλοντικές συνθήκες όπως το pΗ και την ιοντική ισχύ. Τέτοια σωματίδια μπορούν να χρησιμοποιηθούν για παροχή φαρμάκου με καλή σταθερότητα σε φυσιολογικές συνθήκες που μπορεί να οδηγηθεί μέσω της ροής του αίματος. Επιπλέον, η ευαισθησία στο pΗ των συστημάτων αυτών τα καθιστά εξαιρετικούς υποψηφίους για θεραπεία του καρκίνου, όπου οι διαφορές στο pH μεταξύ καρκινικών και φυσιολογικών κυττάρων μπορούν να δώσουν ιδέες για απελευθέρωση στοχευόμενου φαρμάκου. / This study concerns the design of protein/polyelectrolyte mixtures for complexion at physiological conditions. The concept herein involves bovine serum albumin (BSA) complexes with a set of cationic homopolymers and copolymers of poly (MAPTAC)-co -poly (N, N-dimethylacrylamide), with different molecular weight and composition in poly (N, N-dimethylacrylamide) (PDMAM) groups. UVVIS spectrometry, Light Scattering measurements and zeta-potential were involved in the characterization of the aggregates as a function of charge ratio r +/- , pH and ionic strength. The results revealed the formation of oppositely charged complexes, at pH higher than 4.9, the isoelectric point of BSA. Such particles were found dependent on the charge density of the protein surface which strongly influences the electrostatic interactions. As a result, for a PMAPTAC homopolymer the formation of insoluble complexes is favored for high pH values, where the surface charge density of the protein is maximum. Contrarily, enhancement of ionic strength conditions had led to suppression of long-range repulsion between polycation and protein negative domains due to electrostatic screening effects. The differences in the complexation were confirmed by comparing two PMAPTAC homopolymers with different molecular weights at constant pH. These aggregates showed differences in size and surface properties dictated by the charge density of the polyelectrolyte. Thus, larger particles were obtained from the polycation with higher molecular weight at pH 7.4. Interestingly, the rate of BSA consumption for polyelectrolyte formation was identical for all the occasions of pH leading to the conclusion that the consumption of BSA is independent of pH. Addition of neutral hydrophilic PDMAM extended the possible complexation mechanism. By comparing a set of copolymers bearing different content of hydrophilic DMAM groups, only soluble polyelectrolyte/ protein complexes were formed with hydrodynamic sizes < 50 nm. This behavior has been ascribed to the presence of the hydrophilic DMAM units that acts as a protective hydrated outer shell of the aggregates refraining further aggregation. Accordingly, the complexes formed from the copolymer with the different DMAM content have shown 2 stronger protein affinity for the copolymer with the lowest DMAM content. This illustrates the importance of hydrophilic groups which sterically hinder the access and/or exposure of ions to the surface of the complex. Thus the hydrophilic outer shell is either shorter or less dense, fact that allows rearrangement of the particles so that more charges are present on the surface of the aggregate that can further interact with the cationic polyelectrolyte. Thus, the system presented herein represents an in depth study of possible mechanisms of polyelectrolyte interactions with proteins. Furthermore, the formation of nano-scaled complexes stable in aqueous solution was achieved by tuning molecular parameters such as molecular weight, charge ratio and hydrophilic/hydrophobic balance. Additionally, the systems had presented responsiveness to environmental stimuli such as pH and ionic strength. Such particles can be used for drug delivery with good stability at physiological conditions which can lead to long circulation in the blood stream. Moreover, the pH sensitivity of these systems makes them excellent aspirants for cancer therapy where differences in tumor and normal cell pH is a concept for targeted drug delivery.

The photophysics and thermal properties of a series of seven novel triarylamine (TAA) dyes are described. Fluorescence characteristics have been studied in solvents of various polarities at room temperature and at 77 K. High molar extinction coefficients of the magnitude of 3.0-4.0(+/-0.50)x104 M-1cm-1 were obtained for most compounds, and relatively short radiative lifetimes were observed. Fluorescence quantum yields of the dyes at room temperature in cyclohexane were found to be between 0.34-0.57 increasing to 0.67-0.95 at 77 K. It has been shown that while at room temperature, solvent shell relaxation around the excited state can occur, and emission is from an equilibrium excited state to a twisted ground state, at 77 K in a rigid matrix environment solvent shell relaxation cannot occur and emission is from a Franck-Condon excited state to a planar ground state. The TAAs studied have excellent thermal properties for possible use in devices with thermal decomposition temperatures of greater than 300 &deg;C, they also do not crystallise readily. Three poly (9,9-bis[N,N-(trimethylammonium)hexyl] fluorene-co-l,4-phenylene), fluorescent cationic conjugated polymers (CCP), of average chain lengths- 6, 12 and 100 repeat units, and their interaction with DNA and guanine are reported. Fluorescence microscopy and atomic force microscopy have been utilised to visualise the interaction between the polymers and DNA. Results show both efficient compaction of DNA induced by the polymer and linking and bridging of DNA/polymer aggregates. CCPs are known to aggregate in water, and for the CCPs studied here this is reflected in a decrease in fluorescence. These aggregates can be broken up by mixtures of solvents, e.g. acetonitrile/water. Steady state and ps time resolved techniques have been used to study: (i) aggregation of CCPs in various acetonitrile/water mixtures, and (ii) fluorescence quenching by single and double strand DNA, and guanine. All CCPs are extremely sensitive to quenching by DNA or guanine, with sensitivity increasing with chain length of both the CCP and DNA. Stem-Volmer plots are sigmoidal and have initial quenching rates constants far in excess of the diffusion controlled limit. The results have been analysed in terms of energy migration and trapping within and between polymer chains. Quenching seems best analysed in terms of an equilibrium in which a CCP/DNA aggregate complex is formed which brings polymer chains into close enough proximity to allow interchain excitation energy migration and quenching at aggregate or DNA base traps. We also report preliminary results of modelling time resolved data, of both the aggregation and quenching, using a kinetic model in which energy migration and trapping are represented as a series of energy transfer steps between neighbours.

The main aim of the diploma thesis is to investigate the influence of incorporated polyelecrolyte additives on the mechanical and transport properties of hydrogel. Hydrogels, based on polyvinylalcohol, were selected for these experiments. Gelation of polyvinylalcohol can be induced physically or chemically. The aim was to investigate the influence of sodium alginate, sodium polystyrene sulfonate and sodium polyglutamate. Mechanical properties were studied by rheology, through viscoelastic properties. Transport properties were analyzed by using two methods: diffusion pair and fluorescence correlation spectroscopy.

Polymer electrolytes, ionic monomers catenated into a macromolecule, have received a considerable attention in the past decade as they combine the mechanical benefits of flexible chain with the ionic properties of liquid electrolytes. For this reason, they have been widely accepted as potential ion conducting membrane candidates for electrolyzers, energy storage devices, and desalination applications. In efforts to improve the efficiency of polymer electrolyte separators a block copolymer paradigm has been employed. This material’s strategy allows for a spatial separation of the components that control the mechanical and electrochemical properties and thus enables independent engineering of each. Charge – neutral block copolymers (CN-BCPs), a diblock copolymer containing a polyelectrolyte block, attempt to leverage this paradigm, however, to date, the impact ions have on the CN-BCP self-assembly is still an open question. In this dissertation, we are devoted to uncovering the fundamental impact of ionic interactions on CN-BCP self-assembly in bulk and thin-films. First, we survey the literature and compile a list of thoroughly investigated CN-BCPs (derived from imidazolium, quaternary ammonium, and phosphonium motifs) with known dielectric properties. The ionic interaction strength for each CN-BCP was determine using the polyelectrolyte block’s static dielectric constant (ε_r) and the definition of the Bjerrum length (l_B=e^2⁄(4πε_0 ε_r k_b T)). The CN-BCPs studied in the literature, copolymers containing polyelectrolytes blocks with a high ε_r, display a morphology diagram akin to what is expected from the traditional block copolymer self-assembly. However, using a suite of experiment characterization techniques we show that CN-BCPs that contain a polyelectrolyte block with a low static dielectric constant (ε_r=2.5) produce an asymmetric morphology diagram. In this case, we find morphologies that would assemble the polyelectrolyte block into a discrete phase are suppressed if not completely absent. To explain this usual result, we invoke a simple free energy argument, geometric analysis, and a packing parameter model derived from small molecule surfactant principles to rationalize the asymmetry in the morphology diagram on a basis of long-range ionic correlations. Utilizing the packing parameter model we were able to quantitively capture the morphology diagrams of all known CN-BCPs using a single interaction energy parameter. Next, we explore the impact of film thickness on CN-BCP self-assembly via solvent vapor annealing thin-films. A complimentary CN-BCP morphology diagram is constructed for a constant film thickness (h=40 nm) and compared to the bulk phase behavior. Similar to the bulk morphology mapping, we found an asymmetric thin-film morphology diagram with only a singular ordered morphology – cylinders. The influences of film confinement are discussed and utilized to reversibly switch the CN-BCP domain orientation on demand. Finally, we use in-situ grazing incidence small angle x-ray scattering to explore the CN-BCP thin-film structural evolution during the solvent vapor annealing process. We find quantitively different processing pathways when nonselective or selective solvents are used to vapor anneal CN-BCPs. A wide range of annealing solvents spanning a ε_r=4.8-32.7 range was chosen to vapor anneal CN-BCP thin films and a relationship between CN-BCP periodicity (d) and ε_r was determined. We find d~1⁄√ε relationship suggesting the CN-BCP periodicity can be engineer by choice of annealing solvent. Additionally, in this dissertation, we explore the broader impact of morphology on the ion transport through polymer electrolyte membranes. In this vein, we propose structure – property relationships that will enable a rational design of single-ion conducting separators. Using in-house electrochemical techniques, nanoindentation, and gravimetric analysis we explore the relationship between ionic selectivity, quantified through the counterion transference number (t_c^m), the ionic conductivity (κ), and the separator hardness with respect to separator water volume fraction ( ϕ_(H_2 O)). We find t_c^m increases with increasing separator swollen-state charge density which is consistent with a donnan repulsion perspective. Additionally, as ϕ_(H_2 O) increases we find κ increases by orders of magnitude indicting that hydration plays an intimate role in improving ion diffusion in polymer electrolytes. Finally, we present a summary of the permselectivity, Ψ^m=(〖(t〗_c^m-t_c^aqu))⁄((1-t_c^aqu)) , where t_c^aquis equivalent to the aqueous transference number, to κ for a series of polymer electrolytes characterized in literature. We find that separators derived from polymers with rigid backbones (e.g. poly(phenyl sulfone) and poly(2,6-dimethyl-1,4-phenylene oxide)) tend to have a small tradeoff between Ψ^m and κ yet cannot access ideal counterion selectivity (Ψ^m=1) when κ→0. As the backbone flexibility increases the Ψ^m- κ tradeoff is more dramatic yet a Ψ^m=1 when κ→0 is recovered suggesting the importance of molecular packing in this regime. We thus conclude that designing separators with an ideal Ψ^m- κ relationship will require a simultaneous manipulation of molecular architecture, separator hydration state, and morphology.

Submitted to the faculty of Indiana University In partial fulfillment of the requirements for the degree Master in Bioinformatics In the School of Informatics, Indiana University, December 2004 / The aggregation rate of B-Lactoglobulin (BLG) was studied using turbidimetry and dynamic light scattering in the range 5.8<pH,3.5 at a fixed ionic strength of 4.5 mM, and in the range 4.5 - 500mM NACl at a fixed pH of 5.0. The initial slope of turbidity vs time curve was used to define an initial rate. The highest initial rates of aggregation were observed in the pH range 4.50 to 4.75 but the increase in aggregation rate when the pH was reduced from 5.0 to 4.69 was large compared to its decrease when the pH was reduced from pH 4.69 to 4.20; i.e. the dependence of initial rate on pH was highly asymmetric. The rate of aggregation at pH 5.0 strongly increased with decrease in ionic strength I from 100 to 4.5 mM and was found to be nearly linear with 1/ I. QELS measurements at pH 5.22 and 5.40 at I = 4.5mM revealed that particle size increased with time. Eventual appearances of bimodal distributions showed fast and slow modes corresponding to the BLG dimer and to hydrodynamic diameter 100-800 nm. Measurements at 4.0 and 4.2 indicated the consumption of dimers in the first few minutes to form higher order aggregates. Electrostatic modeling via Delphi was used to visualize the electrostatic poetnetial around the BLG dimer in order to elucidate the pH and ionic strength dependence of BLG aggregation rates. The aggregation process appears to comprise firstly an initial fast consumption of dimer, whose dependence on pH and I arises from the interaction of the positive and negative domains of interacting dimers; and secondly, the slow formation of much larger aggregates with relatively little sensitivity to pH and I. The open-ended nature of BLG aggregation is thought to arise from the asymmetry of the dimer charge distribution in the range 4.2<pH<5.2. Polyanions appear to inhibit aggregation. However, the role of polyanions in minimizing BLG aggregation was observed immediately after the addition of polyanioin to the protein. / Bioinformatics

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<p> Water soluble polymers are used as flocculants in wastewater treatment, mineral processing, and pulp and paper production. The work in this thesis focuses on the synthesis of graft polyelectrolytes and the efficiency of the copolymers in flocculation. It was proposed that it would be advantageous to have clusters of high charge that can adsorb strongly to the particle surface, and a long chain of nonionic polymer to bridge the particles together.</p> <p> Electrolyte copolymers were produced using a high molecular weight polyacrylamide as the backbone polymer and a redox agent, ceric ammonium nitrate, to form a radical site on the polymer. DADMAC monomer was polymerized from these radical sites producing grafts of cationic charge. The copolymers were produced at a range of polymerization conditions including PAM concentration, amount of nitric acid, amount of ceric ion and polymerization temperature. Grafting was successful and homopolymerization of DADMAC was found not to occur. The graft polymers were characterized using NMR, charge titration, viscosity measurements, and gel fraction measurements.</p> <p> The copolymers were tested for flocculating properties using a model TiO2 system. The graft copolymers produced performed better than the backbone polyacrylamide, low and high molecular weigh polyDADMAC, and a commercial random copolymer of acrylamide and DADMAC. It was found that both the amount of charge and gel is very important in flocculation performance. However, the testing of the copolymers as a conditioner for a municipal sludge did not show improvement in the drainage rate.</p> / Thesis / Master of Engineering (MEngr)