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Case: A 15-month-old boy who was being followed for developmental dysplasia of the hip because of breech presentation was discovered to have a solitary infantile myofibroma in the left femoral neck. The patient was avoiding weight-bearing on the affected extremity; thus, stabilization of the femoral neck was performed using a proximal femur locking plate. Postoperatively, he achieved all gross motor developmental milestones. Conclusion: This report is the first to describe a solitary infantile myofibroma in the femoral neck and demonstrates the utility of operative stabilization of these lesions. [ABSTRACT FROM AUTHOR]

Our understanding of molecules has stagnated at a single quantum system, with atoms as Newtonian particles and electrons as quantum particles. Here, however, we reveal that both atoms and electrons in a molecule are quantum particles, and their quantum–quantum interactions create a previously unknown, newfangled molecular property—supracence. Molecular supracence is a phenomenon in which the molecule transfers its potential energy from quantum atoms to photo-excited electrons so that the emitted photon has more energy than that of the absorbed one. Importantly, experiments reveal such quantum energy exchanges are independent of temperature. When quantum fluctuation results in absorbing low-energy photons, yet still emitting high-energy photons, supracence occurs. This report, therefore, reveals novel principles governing molecular supracence via experiments that were rationalized by full quantum (FQ) theory. This advancement in understanding predicts the super-spectral resolution of supracence, and molecular imaging confirms such innovative forecasts using closely emitting rhodamine 123 and rhodamine B in living cell imaging of mitochondria and endosomes. [ABSTRACT FROM AUTHOR]

Abstract: Studies show that medical school curriculums do not prepare graduates to manage the most common musculoskeletal (MSK) injuries they will encounter in the outpatient setting. The authors proposed a new multiple-choice assessment to identify individual and program deficiencies for curriculum improvement. A multiple-choice MSK assessment tool was administered to learners at various stages of training. Students took the examination after completing their core clerkship year; residents took the examination near the beginning of their respective academic year. Outcome measures included average examination score, percent correct for each question, and overall examination reliability. Average examinees scores were 75.6% with higher scores based on training years. No statistical differences were found between MD/DO, male/female, or military/civilian examinees. The tool was found to be a statistically valid method of determining cognitive knowledge in basic MSK topics, identifying individual deficiencies, and highlighting gaps in training programs' MSK curriculums. [ABSTRACT FROM AUTHOR]

Monitoring multiple molecular probes simultaneously establishes their correlations and reveals the holistic mechanism. Current fluorescence imaging, however, is limited to about four colors because of typically circa 100‐nm spectral width. Herein, we show that molecular supracence imparts superior spectral resolution, resolving eight colors in 300‐nm width, about 37.5‐nm per color. A recently discovered light‐molecule interacting phenomenon, supracence only measures molecular emission above its excitation energy due to entanglement between atomic quantum system and electronic quantum system. As such, supracence takes advantage of sharp spectral edge of a single pathway and excitation specificity to produce narrow bands, whereas fluorescence has to deal with multiple pathways spilling out low‐energy long tail, that causes poor resolution. Thus, supracence enables myriad innovative molecular spectroscopy and microscopic imaging with profound impact broadly. [ABSTRACT FROM AUTHOR]

The currently understood principles about light–molecule interactions are limited, and thus scientific scope beyond current theories is rarely harvested. Herein we demonstrate supracence phenomena, in which the emitted photons have more energy than the absorbed photons. The extra energy comes from couplings of the absorbed and emitted photon to molecular phonons, whose potentials are constantly exchanging with molecular quantum energy and the environment. Thus, supracence is a linear optical process rather than a nonlinear optical process, such as second harmonic generation. Because supracence results in cooled molecular phonons and thus cooled molecules, behavior opposite to that of hot fluorescing emitters is expected. This report reveals certain supracence principles while contrasting fluorescence with supracence in high‐resolution imaging. [ABSTRACT FROM AUTHOR]

Folding–unfolding imparts fluorescence dual color switching, thus a novel concept to switch fluorescence between two distinct colors while avoiding traditional bond rupturing and bond forming in photoswitching. Because folding and unfolding minimize the wear and tear on molecular structures, the new systems have excellent reversibility and fatigue resistance. [ABSTRACT FROM AUTHOR]

Photoswitching of bis(dithiazole)ethene can be regulated by Hg(II) ions and EDTA in a "lock-and-unlock" manner. The molecular photoswitch provides an enzyme-like binding pocket that selectively binds specifically to mercury ions, thus modulating the degree of photoswitching in its presence. [ABSTRACT FROM AUTHOR]

The fluorescence brightness of a molecular probe determines whether it can be effectively measured and its water solubility dictates if it can be applied in real-world biological systems. However, molecules brighter than the most efficient fluorescent dyes or particles brighter than quantum dots are hard to come by, especially when they must also be soluble in water. In this report, chromophoric phosphoramidites are used in a solid-state synthesis to construct functional dendrimers. When highly twisted chromophores are chosen and the proper spacers and dendrons are introduced, the resultant dendrimers emit exceptionally bright fluorescence. Chromophores, spacers, and dendrons are stitched together by efficient phosphoramidite reagents, which afford high-yield water-soluble phosphodiester linkages after deprotection. The resulting water-soluble dendrimers are exceptionally bright. [ABSTRACT FROM AUTHOR]

Using one ray of light to encode another ray of light is highly desirable because information in optical format can be directly transferred from one beam to another without converting back to the electronic format. One key medium to accomplish such an amazing task is photoswitchable molecules. Using bis(dithiazole)ethene that can be photoswitched between its ring‐open and ring‐closed states quantitatively with excellent fatigue resistance and high thermal stability, it is shown that quantitative photoreversibility allowed the photoswitching light to control other light travelling through the photoswitchable medium, a phenomenon of transferring information encoded in one light ray to others, thus imparting photo‐optical modulation on the orthogonal light beam. [ABSTRACT FROM AUTHOR]

Optical microscopy has been an ideal tool for studying phenomena in live cells because visible light at reasonable intensity does not perturb much of the normal biological functions. However, optical resolution using visible light is significantly limited by the wavelength. Overcoming this diffraction-limit barrier will reveal biological mechanisms, cellular structures, and physiological processes at a nanometer scale, orders of magnitude lower than current optical microscopy. Although this appears to be a daunting task, recently developed photoswitchable probes enable reconstruction of individual images into a super-resolution image, thus the emergence of nanoscopy. Harnessing the resolution power of nanoscopy, we report here nano-resolution fluorescence imaging of microtubules and their network structures in biological cells. The super-resolution nanoscopy successfully resolved nanostructures of a microtubule network―a daunting task that cannot be completed using conventional wide-field microscopy. [ABSTRACT FROM AUTHOR]

Core-shell polymeric nanoparticles (NPs) containing photoswitchable spiropyrans (SP) and spirooxazines (SO) within the cores were fabricated. Fluorescence photoswitching studies revealed that the substituent groups on the photochromic SP/SO structures exerted significant influence on the fluorescence photoswitching behaviors of the as-prepared polymeric NPs, such as the reversibly interchangeable fluorescence color and the photoswitching kinetics. The electron-releasing and electron-withdrawing abilities of the substituent groups are believed to play important roles in controlling the electron configuration of the photochromic component and therefore be responsible for the tunable dual-color photoswitching performance. [ABSTRACT FROM AUTHOR]

Because of its ultrasensitivity, fluorescence offers a noninvasive means to investigate biomolecular mechanisms, pathways, and regulations in living cells, tissues, and animals. However, real-world applications of fluorescence technologies encounter many practical challenges. For example, the intrinsic heterogeneity of biological samples always generates optical interferences. High background such as autofluorescence can often obscure the desired signals. Finally, the wave properties of light limit the spatial resolution of optical microscopy. [ABSTRACT FROM AUTHOR]

Supramolecular forces govern self-assembly and further determine the final morphologies of self-assemblies. However, how they control the morphology remains hitherto largely unknown. In this paper, we have discovered that the self-assembled nanostructures of rigid organic semiconductor chromophores can be finely controlled by the secondary forces by fine-tuning the surrounding environments. In particular, we used water/methanol/hydrochloric acid to tune the environment and observed five different phases that resulted from versatile molecular self-assemblies. The representative self-assembled nanostructures were nanotapes, nanoparticles and their 1D assemblies, rigid microplates, soft nanoplates, and hollow nanospheres and their 1D assemblies, respectively. The specific nanostructure formation is governed by the water fraction, Rw, and the concentration of hydrochloric acid, [HCl]. For instance, nanotapes formed at low [HCl] and Rw values, whereas hollow nanospheres formed when either the HCl concentration is high, or the water fraction is low, or both. The significance of this paper is that it provides a useful phase diagram by using Rw and [HCl] as two variables. Such a self-assembly phase diagram maps out the fine control that the secondary forces have on the self-assembled morphology, and thus allows one to guide the formation toward a desired nanostructure self-assembled from rigid organic semiconductor chromophores by simply adjusting the two key parameters of Rw and [HCl]. [ABSTRACT FROM AUTHOR]

Photosensitive fluorescent probes have become powerful tools in chemical biology and molecular biophysics, which are used to investigate cellular processes with high temporal and spatial resolution. Accordingly, photosensitive fluorescent probes, including photoactivatable, photoconvertible, and photoswitchable fluorophores, have been extensively developed during the past decade. The photoswitchable fluorophores have received much attention because they highlight cellular events clearly. This minireview summarizes recent advances of using reversibly photoswitchable fluorophores and their applications in innovative bioimaging. Photoswitchable fluorophores include photoswitchable fluorescent proteins, photoswitchable fluorescent organic molecules (dyes), and photoswitchable fluorescent nanoparticles. Several strategies have been developed to synthesize photoswitchable fluorophores, including engineering combination proteins, chemical synthesis, polymerization, and self-assembly. Here we concentrate on polymer nanoparticles with optically switchable emission properties: either fluorescence on/off or dual-alternating-color fluorescence photoswitching. The essential mechanisms of fluorescence photoswitching enable different types of photoswitchable fluorophores to change emission intensity or wavelength (color) and thus validating the basis of the fluorescence on/off or dual-color photoswitching design. Generally the possible applications of any fluorophores are to label biological targets, followed by specific imaging. The newly developed photoswitchable fluorophores enable super-resolution fluorescence imaging because of their photosensitive emission. Finally, we summarize the important area regarding future research and development on photoswitchable fluorescent nanoparticles. [ABSTRACT FROM AUTHOR]

A single probe has limited brightness in time-domain imaging and such limitation frequently renders individual molecules undetectable in the presence of interference or complex cellular structures. However, a single photoswitchable probe produces a signal, which can be separated from interference or noise using photoswitching-enabled Fourier transformation (PFT). As a result, the light-modulated probes can be made super bright in the frequency domain simply by acquiring more cycles in the time domain. [ABSTRACT FROM AUTHOR]

We report a simple approach to synthesize a new class of imide-dipeptides. This approach is mild, and the starting materials are the easily accessible amino acid derivatives. The imide-dipeptides were synthesized from the coupling of an amide and a 4-nitrophenyl activating ester of an amino acid. The acidic proton of the first amide was removed by 1 equivalent of n-butyl lithium to afford the corresponding amide anion which then reacted with the activating ester to give the desired imide derivatives. [ABSTRACT FROM AUTHOR]

Optical imaging in live cells has provided a wealth of information regarding the various biological mechanisms, including using genetically coded green-fluorescent protein-conjugated organic dye molecules and, more recently, highly luminescent quantum dots as optical tags for the target biomolecules. Cells are inherently complex, grow constantly and have autofluorescence covering the entire visible spectrum ranging from green to red. At the single quantum-emitter level, it is often difficult to distinguish optical probes from fortuitous fluorophores inside living cells owing to complexity and constant evolvement. We have developed photoswitchable nanoparticles--optical nanoprobes that can be highlighted in either red or green during fluorescence imaging. Such optically addressable nanoprobes offer unambiguous detection of sites of biological interactions, and successfully implementing such optically switchable nanoprobes should greatly reduce the occurrence of false-positives in biomedical imaging and unambiguous detections. [ABSTRACT FROM AUTHOR]

Using photo-actuated unimolecular logical switching attained reconstruction (PULSAR) nanoscopy, the structures of photoswitchable polymeric nanoparticles self-assembled on the surfaces of CaCl2crystals at the nanoscale were revealed; the photoswitching events and the locations of the photoswitchable fluorescent dyes inside the hydrophobic cores of the core–shell type polymeric nanoparticles were determined. [ABSTRACT FROM AUTHOR]

Polymeric fluorescent nanoparticles with covalently embedded perylene fluorophores were developed by facile synthesis strategy and their advanced features of extremely high fluorescence intensity, non-photoblinking and excellent photostability were experimentally confirmed at the single nanoparticle level. [ABSTRACT FROM AUTHOR]

Unique perylene diastereomeric linear and cyclic dimers were synthesized from twisted perylene monomers, revealing that π-stacking stereoisomerism imparted specific intermolecular self-assembly and intramolecular folding. Only the homochiral twisted tetrachloroperylene monomers cyclized via a cooperative reaction, forming the homochiral diastereomers. The heterochiral tetrachloroperylene monomers proceeded through a stepwise reaction and yielded a linear heterochiral dimer, which equilibrated with the linear homochiral dimers. The linear homochiral dimers cyclized to produce the same cyclic homochiral diastereomers. These results demonstrated that homochiral and heterochiral self-assemblies were two distinct molecular codes, directing two specific chemical pathways. The homochiral cyclic dimers remain isomerically pure at -20 °C but can be interconverted to the heterochiral cyclic dimer meso compound at room temperature. The diastereomers were readily separated by HPLC. While driven by solvophobic forces, foldable linear dimers synthesized from the same twisted monomers using phosphoramidite chemistry folded into homodimer and heterodimer, confirming the inherent molecular codes, which were dictated by the perylene chirality, ultimately gauged the weak π-stack forces, and directed self-assembly and folding. [ABSTRACT FROM AUTHOR]

The article examines the unusual colorful single molecule spectral dynamics during the folding and unfolding of chromophic foldamers. A 488-nanometer line of an argon ion laser and the perylene monomer was used to examine and found that single chromophore spectral fluctuation has occurred due to both conformational and environmental changes. It also stresses the importance of folded biolpoymers such as proteins in the generation of an array of novel biological functions.

We have developed a class of spiropyran dyes and their fluorescence colors can be reversibly photoswitched from red to green, blue, or nearly dark, thus alternating between two colors. Such individual dyes emit either one color or the other but not both simultaneously. Nanoparticles enabled with these photoswitchable dyes, however, emit either one pure color or a combination of both colors because the nanoparticle fluorescence originates from multiple dyes therein. As a result, the nanoparticle shines >30 times brighter than state-of-the-art organic dyes such as fluorescein. Interestingly, these copolymer nanoparticles exhibit tunable nonspecific interactions with live cells, and nanoparticles containing properly balanced butyl acrylate and acrylamide monomers render essentially very little nonspecific binding to live cells. Decorated with HMGA1 protein, these optically switchable dual-color nanoparticles undergo endocytosis and unambiguously identify themselves from fluorescence interference including autofluorescence, thus enabling a new tool for live cell imaging. [ABSTRACT FROM AUTHOR]

Single molecule fluorescence spectroscopy has been used to probe architecturally diverse and unique model oligomers containing exactly two or four perylene tetracarboxylic diimide (PTDI) units: linear foldamers lin2 and lin4, monocyclic complement cyc2, and concatenated foldable rings cat4. Linear, cyclic, and concatenated foldamers reveal that photoabsorption and excitation induces unfolding and refolding, generating colorful spectral switching from one spectral type to another. Foldamer architectures dictate the unfolding and refolding processes, and hence the spectral dynamics. As a result, linear tetramer exhibits active frame-to-frame spectral switching accompanying dramatic changes in colors, but a concatenated tetramer displays a multicolored composite spectrum with little or no spectral switching. Excited state dynamics causes spectral switching: an electronically decoupled PTDI monomer emits green fluorescence while electronically coupled PTDI π-stacks emit red fluorescence, with longer π-stacks emitting redder fluorescence. A key question we address is the excited-state delocalization length, or the exciton coherence length, in the π-stacks, which has been proven difficult to measure directly. Using foldamers having controlled sequences, structures, and well-defined length and chromophore numbers, we have mapped out the exciton coherence length in π-stacks. Single molecule fluorescence studies on chromophoric foldamers reveal that the maximum domain length is delocalized across just four π-stacked PTDI dyes and no new pure color can be found for oligomers beyond the tetramer. Therefore, the range of fluorescent colors in π-stacks is a function of the number of chromophores only up to the tetramer. [ABSTRACT FROM AUTHOR]

We report here that molecular self-assembly can effectively direct and enhance specific reaction pathways. Using perylene π-π stacking weak attractive forces, we succeeded in synthesizing perylene bisimide macrocyclic dimer and a concatenated dimer-dimer ring from dynamic self-assembly of monomeric bis-N,W-(2-(2-(2-(2-thioacetylethoxy)ethoxy)ethoxy)ethyl)perylenetetracarboxylic diimide. The monocyclic ring closure and the dimer-dimer ring concatenation were accomplished through formation of disulfide bonds, which was readily triggered by air oxidization under basic deacetylation conditions. The perylene cyclic dimer and its concatenated tetramer were characterized using both structural methods (NMR, mass spectroscopy) and photophysical measurements (UV-vis spectroscopy). Kinetic analyses offer informative insights about reaction pathways and possible mechanisms, which lead to the formation of complex concatenated rings. Molecular dynamic behaviors of both the monocyclic dimer and the concatenated dimer- dimer ring were modeled with the NWChem molecular dynamics software module, which shows distinct stacking activities for the monocyclic dimer and the concatenated tetramer. [ABSTRACT FROM AUTHOR]

Polymer nanoparticles of 40-400 nm diameter with spiropyran-merocyanine dyes incorporated into their hydrophobic cavities have been prepared; in contrast to their virtually nonfluorescent character in most environments, the merocyanine forms of the encapsulated dyes are highly fluorescent. Spiro-mero photoisomerization is reversible, allowing the fluorescence to be switched "on" and "off" by alternating UV and visible light. Immobilizing the dye inside hydrophobic pockets of nanoparticles also improves its photostability, rendering it more resistant than the same dyes in solution to fatigue effects arising from photochemical switching. The photophysical characteristics of the encapsulated fluorophores differ dramatically from those of the same species in solution, making nanoparticle-protected hydrophobic fluorophores attractive materials for potential applications such as optical data storage and switching and biological fluorescent labeling. To evaluate the potential for biological tagging, these optically addressable nanoparticles have been delivered into living cells and imaged with a liquid nitrogen-cooled CCD. [ABSTRACT FROM AUTHOR]

The article demonstrates that single-molecule spiropyran-to-merocyanine photoswitching imparts strong red fluorescence and that the resulting merocyanine offers good photophysical characteristics. The authors report that such fluorescence photoswitching enables nanometer spatial resolution PULSAR microscopy.

The article discusses the study investigating the reversibility photoswitchable dual-color fluorescent nanoparticles as new tools for live-cell imaging. According to the authors, fluorescent labeling of biomacromolecules and cells has become one of the major tools in the study of structural organization and intra- and intermolecular process within the biological systems.

The article presents information on a hard-and-soft hybrid nanosystem whose fluorescence intensity can be reversibly modulated using specific bandwidths of light. There is considerable current interest within the rapidly expanding field of nanotechnology in integrating hard and soft structures into complex functional nanosystems that have stimuli responsive properties. The study specifically attaches a spiropyran via a thiol-metal linkage to a core-shell semiconductive CdSe/ZnS nanocrystal. Preparation of both the spiropyran and the core-shell nanocrystals is a straightforward procedures.

The article presents the study that investigates the cylindrical superparticles (SPs) properties of semiconductor nanorods. The study was administered by using the synthesis of anisotropic SPs in semiconductor nanorods to assess the presence of photoluminescence and polarization as well as axial direction. The study reveals that the experiment create an anisotropic interparticle as well as repulsive solvophobic interaction that corresponds with linear polarized emission.

The article presents information on a study which reveals that introduction of thermosensitive polymers on to gold nanoparticles become responsive to temperature. Poly(N-isopropylacrylamide) (PPA) exhibits a low critical solution temperature (LCST) transition from 30 to 45 degree Celsius. The polymer is hydrophilic and soluble in water below the LCST, but becomes hydrophobic and forms a macroscopic coacervate phase above that temperature due to the fluctuation of hydrophobic interactions and hydrogen bonding. Conjugation with gold nanoparticles requires that the polymer should bear a thiol group at one terminus. Using S-benzyl dithiobenzoate as the reversible addition-fragmentation chain transfer, researchers prepared a PPA homopolymer terminated with thioester groups. Gold nanoparticles coated with thiol-terminated PPA show remarkable temperature sensitivity as manifested in their optical transmittance switching property at 600 nm.