N-Terminal Charged Residues of Amyloid-ß Peptide Modulate Amyloidogenesis and Interaction with Lipid Membrane.

Interactions of amyloid-ß (Aß) peptides and cellular membranes are proposed to be closely related with Aß neurotoxicity in Alzheimer's disease. In this study, we systematically investigated the effect of the N-terminal hydrophilic region of Aß40 on its amyloidogenesis and interaction with supported phospholipid bilayer. Our results show that modulation of the charge properties of the dynamic N-terminal region dramatically influences the aggregation properties of Aß. Furthermore, our results demonstrate that the N-terminal charged residues play a crucial role in driving the early adsorption and latter remobilization of the peptide on membrane bilayer, and mediating the rigidity and viscoelasticity properties of the bound Aß40 at the membrane interface. The results provide new mechanistic insight into the early Aß-membrane interactions and binding, which may be critical for elucidating membrane-mediated Aß amyloidogenesis in a physiological environment and unravelling the origin of Aß neurotoxicity.

Residue-Specific Dynamics and Local Environmental Changes in Aß40 Oligomer and Fibril Formation.

Elucidating local dynamics of protein aggregation is crucial for understanding the mechanistic details of protein amyloidogenesis. Herein, we studied the residue-specific dynamics and local environmental changes of Aß40 along the course of aggregation by using para-cyanophenylalanine (PheCN ) as a fluorescent and vibrational probe. Our results show that the PheCN residues introduced at various positions all exhibited an immediate decay of fluorescence intensity, indicating a relatively synergistic process in early oligomer formation. The fast decreases in the fluorescence intensities of residues 19 and 20 in the central hydrophobic core region and residue 10 in the N-terminal region suggest that they play crucial roles in the formation of the oligomeric core. The PheCN 4 residue exhibits a remarkably slower decrease in fluorescence intensity, implicating its dynamic conformational characteristics in oligomer and fibril formation. Our results also suggest that the N-terminal residues in fibrils are surrounded by a relatively hydrophobic local environment, as opposed to being solvated.

Effects of the Hydrophilic N-Terminal Region on Aß-Mediated Membrane Disruption.

Amyloidogenesis of amyloid-ß (Aß) peptides is intimately related to pathological neurodegeneration in Alzheimer's disease. Here, we investigated the membrane damage activity of Aß40 and its derivatives that contain mutation at the N-terminal charged residues using a membrane leakage assay. A model 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) phospholipid vesicle encapsulating the fluorescent dye carboxyfluorescein was used in the study. Our results show that the mutations of the N-terminal charged residues of Aß40 significantly affect the peptide-induced membrane leakage. The results suggest that favorable electrostatic interactions of the N-terminal charged residues and the phosphatidylcholine membrane surface are crucial in Aß-mediated membrane permeation. The flexible and charge-rich N-terminal region may play a critical role in directing Aß self-association on the membrane surface and in anchoring and stabilizing the peptide aggregates inserted in the phospholipid membrane, which are closely related with membrane disruption activity of Aß. The results provide new mechanistic insight into the Aß-mediated membrane damage process, which may be critical for understanding the mechanism of Aß neurotoxicity in Alzheimer's disease.

Gold Nanoparticles as a Probe for Amyloid-ß Oligomer and Amyloid Formation.

The process of amyloid-ß (Aß) amyloid formation is pathologically linked to Alzheimer's disease (AD). The identification of Aß amyloids and intermediates that are crucial players in the pathology of AD is critical for exploring the underlying mechanism of Aß aggregation and the diagnosis of the disease. Herein, we performed a gold nanoparticle (AuNP)-based study to detect the formation of Aß amyloid fibrils and oligomers. Our results demonstrate that the intensity of the surface plasmon resonance (SPR) absorption band of the AuNPs is sensitive to the quantity of Aß40 amyloids. This allows the SPR assay to be used for detection and semi-quantification of Aß40 amyloids, and characterization of the kinetics of Aß amyloid formation. Furthermore, our study demonstrates that the SPR band intensity of the AuNPs is sensitive to the presence of oligomers of both Aß40 and an Aß40 mutant, which forms more stable oligomers. The kinetics of the stable oligomer formation of the Aß40 mutant can also be monitored following the SPR band intensity change of AuNPs. Our results indicate that this nanoparticle based method can be used for mechanistic studies of early protein self-assembly and fibrillogenesis.

Leadership and emotions in health care organizations.

PURPOSE: The purpose of this research is to describe the relationship between effective leadership and the leader's own ability to manage his/her emotional state. DESIGN/METHODOLOGY/APPROACH: Discusses the connection between leadership and emotions. Differentiates between management and leadership. FINDINGS: Research findings and conclusions remain in dispute. Types of behavior have been found to be integral to leadership performance. ORIGINALITY/VALUE: The paper has proposed a model for defining and differentiating between leading and managing. Five factors were found to be important to the exercise of leadership.