Differences between Tethered Polyelectrolyte Chains on Bare Mica and Hydrophobically Modified Mica

This study investigates the structures of layers of amphiphilic diblock copolymers of poly(t-butyl styrene)-poly- (styrene sulfonate) (PtBS-PSS) adsorbed on both the bare mica surface (hydrophilic) and an octadecyltriethoxysilane (OTE)-modified mica surface (hydrophobic). When the surface is rendered hydrophobic, the nonsoluble block exhibits stronger interaction with the surface and higher adsorbed masses are achieved. Interaction forces between two such adsorbed layers on both substrates were measured using the surface forces apparatus. The effect of salt concentration (Cs) and molecular weight (N) on the height of the self-assembled layers (L0) was examined in each case. The resulting scaling relationship is in good agreement with predictions of the brush model, L0 ∞ N1.0 in the low-salt limit and L0N-1 ∞ (Cs/σ)-0.32 in the salted regime, when adsorption takes place onto the hydrophobized mica surface. For adsorption on the bare mica surface, L0N-0.7 ∞ Cs -0.17 agrees with the scaling prediction of the sparse tethering model. The results suggest that, on the hydrophilic bare mica surface, the adsorbed amount is not high enough to form a brush structure and only very little intermolecular stretching of the tethered chains occurs; in contrast, the presence of the hydrophobic OTE layer increases the tethering density such that the polyelectrolyte chains adopt a brush conformation.

Allosteric regulation of the primase (DnaG) activity by the clamp-loader (τ) in vitro

During DNA replication the helicase (DnaB) recruits the primase (DnaG) in the replisome to initiate the polymerization of new DNA strands. DnaB is attached to the τ subunit of the clamp-loader that loads the β clamp and interconnects the core polymerases on the leading and lagging strands. The τ–DnaB−DnaG ternary complex is at the heart of the replisome and its function is likely to be modulated by a complex network of allosteric interactions. Using a stable ternary complex comprising the primase and helicase from Geobacillus stearothermophilus and the τ subunit of the clamp-loader from Bacillus subtilis we show that changes in the DnaB–τ interaction can stimulate allosterically primer synthesis by DnaG in vitro. The A550V τ mutant stimulates the primase activity more efficiently than the native protein. Truncation of the last 18 C-terminal residues of τ elicits a DnaG-stimulatory effect in vitro that appears to be suppressed in the native τ protein. Thus changes in the τ–DnaB interaction allosterically affect primer synthesis. Although these C-terminal residues of τ are not involved directly in the interaction with DnaB, they may act as a functional gateway for regulation of primer synthesis by τ-interacting components of the replisome through the τ–DnaB−DnaG pathway.

THE GLYCOPROTEINS OF PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS AND THEIR ROLE IN INFECTION AND IMMUNITY

The porcine reproductive and respiratory syndrome virus (PRRSV) is an economically important pathogen of swine and is known to cause abortion and infertility in pregnant sows and respiratory distress in piglets. PRRSV contains a major glycoprotein (GP5) and three minor glycoproteins (GP2a, GP3, and GP4) on the virion envelope, all of which are required for infectious virus production. To study their interactions amongst each other and with a cellular receptor for PRRSV, CD163, I cloned each of the viral glycoproteins and CD163 in various expression vectors. My studies have shown that while the GP2a, GP3, and GP4 are co-translationally glycosylated, the GP5 is post-translationally glycosylated. By using co-immunoprecipitation (co-IP) assays, strong interaction was demonstrated between GP4 and GP5 proteins, although weak interactions among the other envelope glycoproteins were also detected. Further, GP4 was found to mediate interactions leading to formation of multiprotein glycoprotein complex. My results also show that GP2a and GP4 proteins are the only two GPs that specifically interact with the CD163 molecule and that glycosylation of these GPs is required for efficient interaction. Based on these studies, I have developed an interactome map of the viral GPs and CD163 and have proposed a model of the viral glycoprotein complex and its interaction with CD163. Studies reported here also show that glycan addition at residue 184 (N184) of GP2a, and residues N42, N50, and N131 of GP3 is essential for recovery of infectious virus. Although single site glycosylation mutants of GP4 had no effect on infectious virus production, introduction of double mutations was lethal. The loss of glycan moieties of GP2a, GP3, and GP4 proteins had no effect on host neutralizing antibody production. Overall, I conclude that the PRRSV glycoproteins are co-translationally and post-translationally glycosylated, the GP4 protein is central to mediating interglycoprotein interactions, and along with GP2a, serves as the viral attachment protein that is responsible for interactions with the viral receptor, CD163. Further, glycosylation of GP2a, GP3, and GP4 proteins is required for infectious virus production, efficient interaction with CD163, but does not play any role in neutralizing antibody response in infected animals.

The People's Hour and the Social Gospel: George Howard Gibson's Gilded Age Search for an Organization of the Kingdom of God

Previous studies of the Social Gospel movement have acknowledged the fact that Social Gospelers were involved in multiple social reform movements during the Gilded Age and into the Progressive Era. However, most of these studies have failed to explain how the reform experiences of the Social Gospelers contributed to the development of the Social Gospel. The Social Gospelers’ ideas regarding the need to transform society and their strategies for doing so were largely a result of their personal experiences as reformers and their collaboration with other reformers. The knowledge and insight gained from interaction with a variety of reform methods played a vital role in the development of the ideology and theology of the Social Gospel. George Howard Gibson is exemplary of the connections between the Social Gospel movement and several other social reform movements of the time. He was involved in the Temperance movement, was a member of both the Prohibition Party and the People’s Party, and co-founded a Christian socialist cooperative colony. His writings illustrate the formation of his identity as a Social Gospeler as well as his attempts to find an organization through which to realize the kingdom of God on earth. Failure to achieve the changes he desired via prohibition encouraged him to broaden his reform goals. Like many Midwestern Social Gospelers Gibson believed he had found “God’s Party” in the People’s Party, but he rejected reform via the political system once the Populists restricted their attention to the silver issue and fused with the Democratic Party. Yet his involvement with the People’s Party demonstrates the attraction many Social Gospelers had to the reforms proposed in the Omaha Platform of 1892 as well as to the party’s use of revivalistic language and emphasis on producerism and brotherhood. Gibson’s experimentation with a variety of ways to achieve the kingdom of God on earth provides new insight into the experiences and contributions of lay Social Gospelers. Adviser: Kenneth J. Winkle

A Culture of Relationships: Early Care for Italian and American Children

A culture of childhood is a shared vision – an agreed upon vision – of the needs and rights of children, including ideas about how the people of the community can collectively nurture them and at the same time be renewed by them. In other words, it is a set of values, beliefs, and practices that people have created to guide their way of nurturing young children and their families. The vision is about investing in young children and investing in the supports and relationships that children need to learn and grow, both for the reason that children carry our future and because they carry our hopes and dreams for the future. These hopes and dreams begin with birth. Sensitive, emotionally available parents create the framework for interaction with their children by responding to the baby’s cues, engaging the baby in mutual gazes, and imitating the baby. The baby, born with a primary ability to share emotions with other human beings eagerly joins the relationship dance. The intimate family circle soon widens. Providers, teachers, and directors of early childhood programs become significant figures in children’s lives—implicit or explicit partners in a "relationship dance" (Edwards & Raikes, 2002). These close relationships are believed to be critical to healthy intellectual, emotional, social, and physical development in childhood and adolescence as well. These conclusions have been documented by diverse fields of science, ranging from cognitive science to communication studies and social and personality psychology. Close relationships contribute to security and trust, promote skill development and understanding, nurture healthy physical growth, infuse developing self-understanding and self-confidence, enable self-control and emotion regulation, and strengthen emotional connections with others that contribute to prosocial motivation (Dunn, 1993; Fogel, 1993; Thompson, 1996). Furthermore, many studies showing how relationship dysfunction is linked to child abuse and neglect, aggression, criminality, and other problems involving the lack of significant human connections (Shankoff & Meisels, 2000). In extending the dance of primary relationships to new relationships, a childcare teacher can play a primary role. The teacher makes the space ready--creating a beautiful place that causes everyone to feel like dancing. Gradually, as the dance between them becomes smooth and familiar, the teacher encourages the baby to try out more complex steps and learn how to dance to new compositions, beats, and tempos. As the baby alternates dancing sometimes with one or two partners, sometimes with many, the dance itself becomes a story about who the child has been and who the child is becoming, a reciprocal self created through close relationships.