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Diffusion coefficient measurements are important for many biological and material investigations, such as particle dynamics, kinetics, and size determinations. Amongst current measurement methods, single particle tracking (SPT) offers the unique capability of providing location and diffusion information of a molecule simultaneously while using only femptomoles of sample. However, the temporal resolution of SPT is limited to seconds for single-color labeled samples. By directly imaging three dimensional (3D) diffusing fluorescent proteins and studying the widths of their intensity profiles, we determine the proteins' diffusion coefficients using single protein images of sub-millisecond exposure times. This simple method improves the temporal resolution of diffusion coefficient measurements to sub-millisecond, and can be readily applied to a range of particle sizes in SPT investigations and applications where diffusion coefficient measurements are needed, such as reaction kinetics and particle size determinations.

Protein-surface interactions cause the desirable effect of controlled protein adsorption onto biodevices as well as the undesirable effect of protein fouling. The key to controlling protein-surface adsorptions is to identify and quantify the main adsorption mechanisms: adsorptions that occur (1) while depositing a protein solution onto dry surfaces and (2) after the deposition onto wet surfaces. Bulk measurements cannot reveal the dynamic protein adsorption pathways and thus cannot differentiate between the two adsorption mechanisms. We imaged the interactions of single streptavidin molecules with hydrophobic fused-silica surfaces in real-time. We observed both adsorbed proteins on surfaces and diffusing proteins near surfaces and analyzed their adsorption kinetics. Our analysis shows that the protein solution deposition process is the primary mechanism of streptavidin adsorption onto surfaces at the sub-nanomolar to nanomolar protein concentrations. Furthermore, we found that hydrophilic fused-silica surfaces can prevent the adsorption of streptavidin molecules.

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The Carbon Observatory Instrument Suite, or CARBO, consists of four carbon observing instruments sharing a common instrument bus, yet targeted for a particular wavelength band each with a unique science observation. They are: a) Instrument 1, wavelength centered at 756 nm for oxygen and solar-induced chlorophyll fluorescence (SIF) observations, b) Instrument 2, centered at 1629 nm, for carbon dioxide (CO2) and methane (CH4) observation, c) Instrument 3, centered at 2062 nm for carbon dioxide and d) Instrument 4, centered at 2328 for carbon monoxide (CO) and methane. From low-Earth orbit, these instruments have a field-of-view of 10 to 15 degrees, and a spatial resolution of 2 km square. These instruments have a spectral resolving power ranging from ten to twenty thousand, and can monitor columnaverage dry air mole fraction of carbon dioxide (XCO2) at 1.5 ppm, and methane (XCH4) at 7 ppb. These new instruments will advance the use of immersion grating technology in spectrometer instruments in order to reduce the size of the instrument, while improving performance. These compact, capable instruments are envisioned to be compatible with small satellites, yet modular to be configured to address the particular science questions at hand. Here we report on the current status of the instrument design and fabrication, focusing primarily on Instruments 1 and 2. We will describe the key science and engineering requirements and the instrument performance error budget. We will discuss the optical design with particular emphasis on the immersion grating, and the advantages this new technology affords compared to previous instruments. We will also discuss the status of the focal plane array and the detector electronics and housing. Finally, we report on a new approach – developed during this instrument design process - which enables simultaneous measurement of both orthogonal polarization states (S and P) over the field-of-view and optical bandpass. We believe this polarization sensing capability will enable science observations which were previously limited by instrumental and observational degeneracies. In particular: improved sensitivity to all species, better sensitivity to surface polarization effects, better constraints on aerosol scattering parameters, and superior discrimination of the vertical distribution of gases and aerosols.

Sensing starlight rejected from a coronagraph is essential in stabilizing the telescope pointing and wavefront drift, but performance is degraded for dim stars. Laser Metrology (MET) provides a different, complementary sensing method, one that can be used to measure changes in the alignment of the optics at high bandwidth, independent of the magnitude of the host star. Laser metrology measures changes in the separation of optical fiducial pairs, which can be separated by many meters. The principle of operations is similar to the laser metrology system used in LISA-Pathfinder to measure the in-orbit displacement between two test masses to a precision of ~10 picometers. In closed loop with actuators, MET actively maintains rigid body alignment of the front-end optics, thereby eliminating the dominant source of wavefront drift. In the case of a segmented, active primary mirror, MET provides six degrees of freedom sensing, replacing edge sensors. MET maintains wavefront control even during attitude maneuvers, such as slews between target stars, thereby avoiding the need to repeat time-consuming speckle suppression. These features can significantly improve the performance and observational efficiency of future large-aperture space telescopes equipped with internal coronagraphs. We evaluate MET trusses for various proposed monolithic and segmented space-based coronagraphs and present the performance requirements necessary to maintain contrast drift below 10^-11.