19 research outputs found
Balancing the Initiation and Molecular Recognition Capabilities of Eosin Macroinitiators of Polymerization-Based Signal Amplification Reactions
Coupling polymerization initiators to molecular recognition events provide the ability to amplify these events and detect them using the formation of a cross-linked polymer as an inexpensive readout that is visible to the unaided eye. The eosin-tertiary amine co-initiation system, activated by visible light, has proven utility in this context when an average of three eosin molecules are coupled to a protein detection reagent. The present work addresses the question of how detection sensitivity is impacted when the number of eosin molecules per binding event increases in the range of two to fifteen. Unlike in other initiation systems, a non-monotonic relationship is observed between the number of initiators per binding event and the observed detection sensitivity.Burroughs Wellcome Fund (Career Award at the Scientific Interface)Massachusetts Institute of Technology. James H. Ferry Fund for Innovation in Research Educatio
Evaluating the sensitivity of hybridization-based epigenotyping using a methyl binding domain protein
Hypermethylation of CpG islands in gene promoter regions has been shown to be a predictive biomarker for certain diseases. Most current methods for methylation profiling are not well-suited for clinical analysis. Here, we report the development of an inexpensive device and an epigenotyping assay with a format conducive to multiplexed analysis.David H. Koch Institute for Integrative Cancer Research at MIT (First-year Graduate Fellowship)National Science Foundation (U.S.). Graduate Research FellowshipBurroughs Wellcome Fund (Career Award at the Scientific Interface)National Institute of Environmental Health Sciences (Grant P30-ES002109)Massachusetts Institute of Technology. James H. Ferry Fund for Innovation in Research Educatio
Surface Functionalization of Plastic Surfaces with Non-Biofouling Agarose Film to Develop a Chip-Based Platform
Reactivity of Vinyl-Terminated Self-Assembled Monolayers on Gold: Olefin Cross-Metathesis Reactions
Systematic Study of Fluorescein-Functionalized Macrophotoinitiators for Colorimetric Bioassays
We report a systematic investigation of a set of photoreducible
macrophotoinitiators for use in polymerization-based signal amplification.
To test the dependence of photopolymerization responses on the number
of photoinitiators localized per molecular recognition event, we gradually
increased the number of photoinitiator molecules coupled to a constant
scaffold macromolecule from an average of 7 per polymer to an average
of 168 per polymer. To evaluate the capacity of the macrophotoinitiators
to detect molecular recognition, we coupled neutravidin to these molecules
to recognize biotin-labeled DNA immobilized on biochip test surfaces.
Fluorescein macroinitiators were found to be useful in detecting molecular
recognition above a threshold number of initiators per polymer. Above
this threshold, increasing the number of initiators per macroinitiator
resulted in increased signal strength. These findings demonstrate
the feasibility of increasing the number of photoreducible initiators
per binding event beyond three, the number used in previous studies,
that the initiation reaction remains limiting in the range we investigated,
and that the number of initiators per binding event in this system
has a clear impact on assay sensitivity and signal strength
Surface-initiated, ring-opening polymerization of p-dioxanone from gold and silicon oxide surfaces
Thermal Structural Transitions and Carbon Dioxide Adsorption Properties of Zeolitic Imidazolate Framework‑7 (ZIF-7)
As a subset of the
metal–organic frameworks, zeolitic imidazolate
frameworks (ZIFs) have potential use in practical separations as a
result of flexible yet reliable control over their pore sizes along
with their chemical and thermal stabilities. Among many ZIF materials,
we explored the effect of thermal treatments on the ZIF-7 structure,
known for its promising characteristics toward H<sub>2</sub> separations;
the pore sizes of ZIF-7 (0.29 nm) are desirable for molecular sieving,
favoring H<sub>2</sub> (0.289 nm) over CO<sub>2</sub> (0.33 nm). Although
thermogravimetric analysis indicated that ZIF-7 is thermally stabile
up to ∼400 °C, the structural transition of ZIF-7 to an
intermediate phase (as indicated by X-ray analysis) was observed under
air as guest molecules were removed. The transition was further continued
at higher temperatures, eventually leading toward the zinc oxide phase.
Three types of ZIF-7 with differing shapes and sizes (∼100
nm spherical, ∼400 nm rhombic-dodecahedral, and ∼1300
nm rod-shaped) were employed to elucidate (1) thermal structural transitions
while considering kinetically relevant processes and (2) discrepancies
in the N<sub>2</sub> physisorption and CO<sub>2</sub> adsorption isotherms.
The largest rod-shaped ZIF-7 particles showed a delayed thermal structural
transition toward the stable zinc oxide phase. The CO<sub>2</sub> adsorption
behaviors of the three ZIF-7s, despite their identical crystal structures,
suggested minute differences in the pore structures; in particular,
the smaller spherical ZIF-7 particles provided reversible CO<sub>2</sub> adsorption isotherms at ∼30–75 °C, a typical
temperature range of flue gases from coal-fired power plants, in contrast
to the larger rhombic-dodecahedral and rod-shaped ZIF-7 particles,
which exhibited hysteretic CO<sub>2</sub> adsorption/desorption behavior
Thermosensitive Structural Changes and Adsorption Properties of Zeolitic Imidazolate Framework‑8 (ZIF-8)
We compared four types of ZIF-8 with
varying sizes and shapes to
determine their thermal-structural stability and derive appropriate
thermal activation conditions and correlation between structural characteristics
and adsorption properties. Under air, the ZIF-8 phase for all the
samples was converted completely into the zinc oxide phase above ∼300
°C, though thermalgravimetric analysis (TGA) indicated that the
original structure was stable to ∼300–350 °C. Longer
exposures (∼30 d) suggested that thermal activation at ∼200
°C was appropriate for the removal of guest and/or solvent molecules
under air without structural damage. Despite no noticeable change
in X-ray diffraction (XRD) patterns after activation at 250 °C
under air, the resulting BET surface areas and CO<sub>2</sub> adsorption
amounts (at 1 bar and 30 °C) of ZIF-8s were reduced to ∼44–54
and ∼72–87%, respectively, as compared to those of appropriately
activated ZIF-8s. It appears that after the activation at 250 °C
under air, some Zn and N atoms were dissociated and converted to ZnOH
and NOH, respectively, causing the partial structural damage of ZIF-8s