38 research outputs found
Electron multiplication CCD detector technology advancement for the WFIRST-AFTA coronagraph
The WFIRST-AFTA (Wide Field InfraRed Survey Telescope-Astrophysics Focused Telescope Asset) is a NASA space observatory. It will host two major astronomical instruments: a wide-field imager (WFI) to search for dark energy and carry out wide field near infrared (NIR) surveys, and a coronagraph instrument (CGI) to image and spectrally characterize extrasolar planets. In this paper, we discuss the work that has been carried out at JPL in advancing Electron Multiplying CCD (EMCCD) technology to higher flight maturity, with the goal of reaching a NASA technology readiness level of 6 (TRL-6) by early-to-mid 2016. The EMCCD has been baselined for both the coronagraph's imager and integral field spectrograph (IFS) based on its sub-electron noise performance at extremely low flux levels - the regime where the AFTA CGI will operate. We present results from a study that fully characterizes the beginning of life performance of the EMCCD. We also discuss, and present initial results from, a recent radiation test campaign that was designed and carried out to mimic the conditions of the WFIRST-AFTA space environment in an L2 orbit, where we sought to assess the sensor's end of life performance, particularly degradation of its charge transfer efficiency, in addition to other parameters such as dark current, electron multiplication gain, clock induced charge and read noise
Technology advancement of the CCD201-20 EMCCD for the WFIRST coronagraph instrument: sensor characterization and radiation damage
The Wide Field InfraRed Survey Telescope-Astrophysics Focused Telescope Asset (WFIRST-AFTA) mission is a 2.4-m class space telescope that will be used across a swath of astrophysical research domains. JPL will provide a high-contrast imaging coronagraph instrumentâone of two major astronomical instruments. In order to achieve the low noise performance required to detect planets under extremely low flux conditions, the electron multiplying charge-coupled device (EMCCD) has been baselined for both of the coronagraphâs sensorsâthe imaging camera and integral field spectrograph. JPL has established an EMCCD test laboratory in order to advance EMCCD maturity to technology readiness level-6. This plan incorporates full sensor characterization, including read noise, dark current, and clock-induced charge. In addition, by considering the unique challenges of the WFIRST space environment, degradation to the sensorâs charge transfer efficiency will be assessed, as a result of damage from high-energy particles such as protons, electrons, and cosmic rays. Science-grade CCD201-20 EMCCDs have been irradiated to a proton fluence that reflects the projected WFIRST orbit. Performance degradation due to radiation displacement damage is reported, which is the first such study for a CCD201-20 that replicates the WFIRST conditions. In addition, techniques intended to identify and mitigate radiation-induced electron trapping, such as trap pumping, custom clocking, and thermal cycling, are discussed
Aniqsaaq (To Breathe): Study protocol to develop and evaluate an Alaska Native family-based financial incentive intervention for smoking cessation
Background
Alaska Native and American Indian (ANAI) communities in Alaska are disproportionately affected by commercial tobacco use. Financial incentive interventions promote cigarette smoking cessation, but family-level incentives have not been evaluated. We describe the study protocol to adapt and evaluate the effectiveness and implementation of a remotely delivered, family-based financial incentive intervention for cigarette smoking among Alaskan ANAI people.
Methods
The study has 3 phases: 1) qualitative interviews with ANAI adults who smoke, family members, and stakeholders to inform the intervention, 2) beta-test of the intervention, and 3) randomized controlled trial (RCT) evaluating intervention reach and effectiveness on verified, prolonged smoking abstinence at 6- and 12-months post-treatment. In the RCT, adult dyads (ANAI person who smokes [index participant] and family member) recruited throughout Alaska will be randomized to a no-incentives control condition (n = 328 dyads) or a 6-month incentive intervention (n = 328 dyads). All dyads will receive cessation support and family wellness materials. Smoking status will be assessed weekly for four weeks and at three and six months. Intervention index participants will receive escalating incentives for verified smoking abstinence at each time point (maximum $750 total); the family member will receive rewards of equal value.
Results
A community advisory committee contributed input on the study design and methods for relevance to ANAI people, particularly emphasizing the involvement of families.
Conclusion
Our study aligns with the strength and value AIAN people place on family. Findings, processes, and resources will inform how Indigenous family members can support smoking cessation within incentive interventions.Ye
Thermodynamic insight into the interaction mechanism of an ESIPT drug with a serum transport protein: Slower solvent-relaxation dynamics explored through wavelength-sensitive fluorescence behavior
Recently, 3,5-diiodosalicylic acid (3,5-DISA) has garnered enormous research attention owing to its wide-spread medicinal/biological applications, use as a model to study the role of halogen bonding in drug-protein interaction and so forth. However, the arena of the study of interaction of 3,5-DISA with relevant biological targets, particularly serum transport protein still starves for meticulous exploration of a number of fundamental aspects, such as, the thermodynamics and strength of binding, effect of drug binding on the native protein conformation and functionality, rotational and solvent-relaxation dynamics within the protein scaffolds etc. The present investigation endeavors to unveil these important aspects of 3,5-DISA:HSA interaction scenario. Our spectroscopic results demonstrate a remarkable modification of the excited-state intramolecular proton transfer (ESIPT) photophysics of 3,5-DISA upon interaction with HSA. A detailed isothermal titration calorimetry (ITC) study reveals that the interaction process is governed by favorable enthalpic (âH0 < 0) and unfavorable entropic (TâS0 < 0) contributions. The modulation of the hydration structure at the interfaces accompanying the binding phenomenon is also delineated in this context. Circular dichroism (CD) spectroscopy has been exploited to show the slight perturbation of the native protein conformation as a result of drug binding. In complementarity, the functionality of HSA (in terms of esterase-like activity) has also been shown to decrease with added 3,5-DISA. Our cumulative exploration of the wavelength-sensitive fluorescence parameters including red-edge excitation shift (REES) points out a remarkably slower rate of solvent-relaxation dynamics of the HSA-bound 3,5-DISA in the photoexcited state. The modification of the rotational-relaxation behavior of 3,5-DISA within the protein is also addressed and rationalized on the basis of the two-step and wobbling-in-cone model
Interaction of Bile Salts with βâCyclodextrins Reveals Nonclassical Hydrophobic Effect and EnthalpyâEntropy Compensation
Herein,
we present an endeavor toward exploring the lacuna underlying
the host:guest chemistry of inclusion complex formation between bile
salt(s) and β-cyclodextrin(s) (βCDs). An extensive thermodynamic
investigation based on isothermal titration calorimetry (ITC) demonstrates
a dominant contribution from exothermic enthalpy change (Î<i>H</i> < 0) accompanying the phenomenon of inclusion complex
formation, along with a relatively smaller contribution to total free
energy change from the entropic component. However, the negative heat
capacity change (Î<i>C</i><sub>p</sub> < 0) displays
the hallmark for a pivotal role of hydrophobic effect underlying the
interaction. Contrary to the classical hydrophobic effect, such apparently
paradoxical thermodynamic signature has been adequately described
under the notion of ânonclassical hydrophobic effectâ.
On the basis of our results, the displacement of disordered water
from hydrophobic binding sites has been argued to mark the enthalpic
signature and the key role of such interaction forces is further corroborated
from enthalpyâentropy compensation behavior showing indication
for almost complete compensation. To this end, we have quantified
the interaction of two bile salt molecules (namely, sodium deoxycholate
and sodium glycocholate) with a series of varying chemical substituents
on the host counterpart, namely, βCD, (2-hydroxypropyl)-βCD,
and methyl βCD
Binding Interaction of a Prospective Chemotherapeutic Antibacterial Drug with βâLactoglobulin: Results and Challenges
This
Article reports a detailed characterization of the binding
interaction of a potential chemotherapeutic antibacterial drug, norfloxacin
(NOF), with the mammalian milk protein β-lactoglobulin (βLG).
The thermodynamic parameters, Î<i>H</i>, Î<i>S</i>, and Î<i>G</i>, for the binding phenomenon
as-evaluated on the basis of vanât Hoff relationship reveal
the predominance of electrostatic/ionic interactions underlying the
binding process. However, the drug-induced quenching of the intrinsic
tryptophanyl fluorescence of the protein exhibits intriguing characteristics
on SternâVolmer analysis (displays an upward curvature instead
of conforming to a linear regression). Thus, an extensive time-resolved
fluorescence spectroscopic characterization of the quenching process
has been undertaken in conjugation with temperature-dependent fluorescence
quenching studies to unveil the actual quenching mechanism. The invariance
of the fluorescence decay behavior of βLG as a function of the
quencher (here NOF) concentration coupled with the commensurate dependence
of the drugâprotein binding constant (<i>K</i>) on
temperature, the drug-induced fluorescence quenching of βLG
is argued to proceed through static mechanism. This postulate is aided
further support from absorption, fluorescence, and circular dichroism
(CD) spectral studies. The present study also throws light on the
important issue of drug-induced modification in the native protein
conformation on the lexicon of CD, excitationâemission matrix
spectroscopic techniques. Concurrently, the drugâprotein interaction
kinetics and the energy of activation of the process are also explored
from stopped-flow fluorescence technique. The probable binding locus
of NOF in βLG is investigated from AutoDock-based blind docking
simulation
Interplay of Multiple Interaction Forces: Binding of Norfloxacin to Human Serum Albumin
Herein, the binding interaction of
a potential chemotherapeutic antibacterial drug norfloxacin (NOF)
with a serum transport protein, human serum albumin (HSA), is investigated.
The prototropic transformation of the drug (NOF) is found to be remarkably
modified following interaction with the protein as manifested through
significant modulations of the photophysics of the drug. The predominant
zwitterionic form of NOF in aqueous buffer phase undergoes transformation
to the cationic form within the protein-encapsulated state. This implies
the possible role of electrostatic interaction force in NOFâHSA
binding. This postulate is further substantiated from the effect of
ionic strength on the interaction process. To this end, the detailed
study of the thermodynamics of the drugâprotein interaction
process from isothermal titration calorimetric (ITC) experiments is
found to unfold the signature of electrostatic as well as hydrophobic
interaction forces underlying the binding process. Thus, interplay
of more than one interaction forces is argued to be responsible for
the overall drugâprotein binding. The ITC results reveal an
important finding in terms of enthalpyâentropy compensation
(EEC) characterizing the NOFâHSA binding. The effect of drug-binding
on the native protein conformation has also been evaluated from circular
dichroism (CD) spectroscopy which unveils partial rupture of the protein
secondary structure. In conjunction to this, the functionality of
the native protein (in terms of esterase-like activity) is found to
be lowered as a result of binding with NOF. The AutoDock-based docking
simulation unravels the probable binding location of NOF within the
hydrophilic subdomain IA of HSA. The present program also focuses
on exploring the dynamical aspects of the drugâprotein interaction
scenario. The rotational-relaxation dynamics of the protein-bound
drug reveals the not-so-common âdip-and-riseâ pattern
How Does Nanoconfinement within a Reverse Micelle Influence the Interaction of Phenazinium-Based Photosensitizers with DNA?
The major focus of the present work
lies in exploring the influence
of nanoconfinement within aerosol-OT (AOT) reverse micelles on the
binding interaction of two phenazinium-based photosensitizers, namely,
phenosafranin (PSF) and safranin-O (SO), with the DNA duplex. Circular
dichroism and dynamic light-scattering studies reveal the condensation
of DNA within the reverse micellar interior (transformation of the
B-form of native DNA to Ď-form). Our results unveil a remarkable
effect of the degree of hydration of the reverse micellar core on
the stability of the stacking interaction (intercalation) of the drugs
(PSF and SO) into DNA; increasing size of the water nanopool (that
is, <i>w</i><sub>0</sub>) accompanies decreasing curvature
of the DNA duplex structure with the consequent effect of increasing
stabilization of the drug:DNA intercalation. The marked differences
in the dynamical aspects of the interaction scenario following encapsulation
within the reverse micellar core and the subsequent dependence on
the size of the water nanopool are also meticulously explored. The
differential degrees of steric interactions offered by the drug molecules
(presence of methyl substitutions on the planar phenazinium ring in
SO) are also found to affect the extent of intercalation of the drugs
to DNA. In this context, it is imperative to state that the water
pool of the reverse micellar core is often argued to approach bulk-like
properties of water with increasing micellar size (typically <i>w</i><sub>0</sub> ⼠10), so that deviation from the bulk
water properties is likely to be minimized in large reverse micelles
(<i>w</i><sub>0</sub> ⼠10). On the contrary, our
results (particularly quantitative elucidation of micropolarity and
dynamical aspects of the interaction) explicitly demonstrate that
the bulk-like behavior of the nanoconfined water is not truly achieved
even in large reverse micelles
Triblock-Copolymer-Assisted Mixed-Micelle Formation Results in the Refolding of Unfolded Protein
The present work
reports a new strategy for triblock-copolymer-assisted
refolding of sodium dodecyl sulfate (SDS)-induced unfolded serum protein
human serum albumin (HSA) by mixed-micelle formation of SDS with polyÂ(ethylene
oxide)-polyÂ(propylene oxide)-polyÂ(ethylene oxide) triblock copolymer
EO<sub>20</sub>PO<sub>68</sub>EO<sub>20</sub> (P123) under physiological
conditions. The steady-state and time-resolve fluorescence results
show that the unfolding of HSA induced by SDS occurs in a stepwise
manner through three different phases of binding of SDS, which is
followed by a saturation of interaction. Interestingly, the addition
of polymeric surfactant P123 to the unfolded protein results in the
recovery of âź87% of its Îą-helical structure, which was
lost during SDS-induced unfolding. This is further corroborated by
the return of the steady-state and time-resolved fluorescence decay
parameters of the intrinsic tryptophan (Trp214) residue of HSA to
the initial nativelike condition. The isothermal titration calorimetry
(ITC) data also substantiates that there is almost no interaction
between P123 and the native state of the protein. However, the mixed-micelle
formation, accompanied by substantial binding affinities, removes
the bound SDS molecules from the scaffolds of the unfolded state of
the protein. On the basis of our experiments, we conclude that the
formation of mixed micelles between SDS and P123 plays a pivotal role
in refolding the protein back to its nativelike state