With the upcoming MAVEN mission, the role of escape in the evolution of the Martian atmosphere is investigated in more detail. This work builds on our previous modeling of the atmospheric impact of the pickup O + sputtering effects for various solar wind parameters, solar EUV intensities, and the surface crustal field distributions. Relationships between the incident ion properties and the ejected hot neutral components, often referred to as atmospheric sputtering, are derived for application to proposed MAVEN ion spectrometer measurements of precipitating O + . We show how our simulation results can be used to constrain the sputtering effects under present conditions and to interpolate toward estimates of sputtering efficiencies occurring in earlier epochs. Present-day sputtering under typical circumstance is estimated to be weak but possibly detectable as an exospheric enhancement. The ultimate goal of estimating the importance of atmospheric sputtering effects on the evolution of the Martian atmosphere can be better deduced by the combining MAVEN measurements with models and the sputtering response relations derived here.

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Herein we report a new series of bifunctional chelators (BFCs) with high affinity for amyloid aggregates, strong binding affinity towards Cu(II) and favorable lipophilicity for potential blood-brain barrier (BBB) penetration. The alkyl carboxylate pendant arms offer up to three orders of magnitude higher binding affinity towards Cu(II) vs. the parent chelating fragment, and can generate fairly stable Cu complexes, including ⁶⁴Cu-radiolabeled compounds. Among the five compounds tested, the ⁶⁴Cu-YW-7 and ⁶⁴Cu-YW-10 complexes exhibit strong and specific staining of amyloid plaques in <i>ex vivo</i> autoradiography studies. Importantly, these compounds have promising partition coefficient (Log D) values of 0.91-1.26 and show moderate brain uptake in biodistribution studies using CD-1 mice. Overall, these BFCs could serve as lead compounds for the development of positron emission tomography (PET) imaging agents for AD diagnosis.

Positron emission tomography (PET), which uses positron-emitting radionuclides to visualize and measure processes in the human body, is a useful noninvasive diagnostic tool for Alzheimer's disease (AD). The development of longer-lived radiolabeled compounds is essential for further expansion of the use of PET imaging in healthcare, and diagnostic agents employing longer-lived radionuclides such as 64 Cu (t 1/2 = 12.7 h, β + = 17%, β − = 39%, electron capture EC = 43%, and E max = 0.656 MeV) can accomplish this task. One limitation of 64 Cu PET agents for neuroimaging applications is their limited lipophilicity due to the presence of several anionic groups needed to ensure strong Cu chelation. Herein, we evaluate a series of neutral chelators containing the 1,4,7-triazacyclononane or 2,11-diaza[3.3]-(2,6)pyridinophane macrocycles that have pyridyl-containing arms incorporating Aβ-peptide-interacting fragments. The crystal structures of the corresponding Cu complexes confirm that the pyridyl N atoms are involved in binding to Cu. Radiolabeling and autoradiography studies show that the compounds efficiently chelate 64 Cu, and the resulting complexes exhibit specific binding to the amyloid plaques in the AD mouse brain sections versus wild-type controls.