9 research outputs found
Why Does Exercise “Triggerâ€? Adaptive Protective Responses in the Heart?
Numerous epidemiological studies suggest that individuals who exercise have decreased cardiac morbidity and mortality. Pre-clinical studies in animal models also find clear cardioprotective phenotypes in animals that exercise, specifically characterized by lower myocardial infarction and arrhythmia. Despite the clear benefits, the underlying cellular and molecular mechanisms that are responsible for exercise preconditioning are not fully understood. In particular, the adaptive signaling events that occur during exercise to “trigger� cardioprotection represent emerging paradigms. In this review, we discuss recent studies that have identified several different factors that appear to initiate exercise preconditioning. We summarize the evidence for and against specific cellular factors in triggering exercise adaptations and identify areas for future study
Chromophore Photoreduction in Red Fluorescent Proteins Is Responsible for Bleaching and Phototoxicity
Red
fluorescent proteins (RFPs) are indispensable tools for deep-tissue
imaging, fluorescence resonance energy transfer applications, and
super-resolution microscopy. Using time-resolved optical spectroscopy
this study investigated photoinduced dynamics of three RFPs, KillerRed,
mRFP, and DsRed. In all three RFPs, a new transient absorption intermediate
was observed, which decays on a microsecond–millisecond time
scale. This intermediate is characterized by red-shifted absorption
at 1.68–1.72 eV (λ<sub>max</sub> = 720–740 nm).
On the basis of electronic structure calculations, experimental evidence,
and published literature, the chemical nature of the intermediate
is assigned to an unusual open-shell dianionic chromophore (dianion-radical)
formed via photoreduction. A doubly charged state that is not stable
in the isolated (gas phase) chromophore is stabilized by the electrostatic
field of the protein. Mechanistic implications for photobleaching,
blinking, and phototoxicity are discussed
Chromophore Photoreduction in Red Fluorescent Proteins Is Responsible for Bleaching and Phototoxicity
Peer reviewe
Optically Modulatable Blue Fluorescent Proteins
Blue
fluorescent proteins (BFPs) offer visualization of protein
location and behavior, but often suffer from high autofluorescent
background and poor signal discrimination. Through dual-laser excitation
of bright and photoinduced dark states, mutations to the residues
surrounding the BFP chromophore enable long-wavelength optical modulation
of BFP emission. Such dark state engineering enables violet-excited
blue emission to be increased upon lower energy, green coillumination.
Turning this green coillumination on and off at a specific frequency
dynamically modulates collected blue fluorescence without generating
additional background. Interpreted as transient photoconversion between
neutral cis and anionic trans chromophoric forms, mutations tune photoisomerization
and ground state tautomerizations to enable long-wavelength depopulation
of the millisecond-lived, spectrally shifted dark states. Single mutations
to the tyrosine-based blue fluorescent protein T203V/S205V exhibit
enhanced modulation depth and varied frequency. Importantly, analogous
single point mutations in the nonmodulatable BFP, mKalama1, creates
a modulatable variant. Building modulatable BFPs offers opportunities
for improved BFP signal discrimination vs background, greatly enhancing
their utility