AFM and SPR studies of protein adsorption at solid/liquid interface

Membrane-like structure formed by surfactant molecules of didodecyldimethylammonium bromide (DDAB) on both HOPG and gold electrodes were studied with AFM and SPR techniques. The study shows that the thickness of the adsorbed layer of DDAB is strongly dependent on the concentration of the vesicle solution. We have also investigated the adsorption of redox protein, Cytochrome c, on graphite electrode with in situ tapping mode AFM. The protein adsorbs spontaneously onto the electrode covered with an adsorbed phosphate layer and forms a uniform monolayer. The adsorbed protein exhibits a reversible electron transfer at 0.17 V (Ag/AgCI) once the electrode potential has been increased to 0.75V. Using surface plasmon resonance spectroscopy we have measured subtle conformational change in protein, Cyt c, due to electron transfer of a single electron on MPA-coated gold electrode. The electron transfer induced change in the resonant angle is about 0.006 deg., which corresponds to ~ 0.2 A decreases in the thickness. This is consistent with that reduced state is more compact than the oxidized state.

Mother-Infant Reciprocity and the Development of Joint Attention in 12 Month Old Infants

Social contingency is the ability to connect social stimuli, such as those behaviors performed by oneself and those performed by others. Detecting social contingencies occurs by means of reciprocity through shared experiences with others. Reciprocity denotes a circumstance in which two individuals participate in a collaborative exchange, and is distinguished from an event in which two individuals engage in separate, unrelated activities. Specifically, reciprocity incorporates joint attention (JA), which occurs when two individuals simultaneously and visually attend to the same item. JA is facilitated by gazing and pointing, whereby one individual initiates the action and the second individual follows suit by, for example, gaze-following. However, little is known about the role the mother may play in the development of JA. The purpose of our study was to investigate social contingency between mothers and infants engaging in dyadic interactions. Thirty-three 12-month-old typically developing infants (M = 12.2, SD = .19; N = 19 males) were filmed for 10 minutes during free play with their mothers and toys provided by an experimenter. Reciprocity was measured by coding mother-infant interactions when a precise chain of events occurred: (1) mother initiated a bid by introducing a toy/activity or request to the infant, (2) infant accepted the bid/request by engaging in play with the given toy/activity, and (3) mother persisted by continuing to engage in play with said toy/activity. We computed a Pearson Correlation to assess the relation between the mothers’ initiations of JA and their infants’ responses to JA. We found a moderately positive correlation between the two variables (r= 0.37, p<.05). Our findings suggest that reciprocity, an important component of social relationships, during parent-infant dyads may serve as a scaffold for joint attention abilities, which have been linked to social and language development.