The non-equilibrium distribution of colloids in a polymer solution under a temperature gradient is studied experimentally. A slight increase of local temperature by a focused laser drives the colloids towards the hot region, resulting in the trapping of the colloids irrespective of their own thermophoretic properties. An amplification of the trapped colloid density with the polymer concentration is measured, and is quantitatively explained by hydrodynamic theory. The origin of the attraction is a migration of colloids driven by a non-uniform polymer distribution sustained by the polymer's thermophoresis. These results show how to control thermophoretic properties of colloids.

Cells of Flavobacterium johnsoniae and of many other members of the phylum Bacteroidetes exhibit rapid gliding motility over surfaces by a unique mechanism. These cells do not have flagella or pili; instead, they rely on a novel motility apparatus composed of Gld and Spr proteins. SprB, a 669-kDa cell-surface adhesin, is required for efficient gliding. SprB was visualized by electron microscopy as thin 150-nm-long filaments extending from the cell surface. Fluorescence microscopy revealed movement of SprB proteins toward the poles of the cell at ∼2 μm/s. The fluorescent signals appeared to migrate around the pole and continue at the same speed toward the opposite pole along an apparent left-handed helical closed loop. Movement of SprB, and of cells, was rapidly and reversibly blocked by the addition of carbonyl cyanide m-chlorophenylhydrazone, which dissipates the proton gradient across the cytoplasmic membrane. In a gliding cell, some of the SprB protein appeared to attach to the substratum. The cell body moved forward and rotated with respect to this point of attachment. Upon reaching the rear of the cell, the attached SprB often was released from the substratum, and apparently recirculated to the front of the cell along a helical path. The results suggest a model for Flavobacterium gliding, supported by mathematical analysis, in which adhesins such as SprB are propelled along a closed helical loop track, generating rotation and translation of the cell body.cell motility | proton motive force | immunofluorescence microscopy | continuous track | left-handed helix C ells of Flavobacterium johnsoniae, and of many other members of the phylum Bacteroidetes, move rapidly over surfaces at speeds of 1-3 μm/s by gliding motility (1). These cells lack flagella and pili, and the mechanism of cell movement is poorly understood. Flavobacterium gliding is thought to rely on motors embedded in the cell envelope that propel large cell-surface adhesins such as SprB and related proteins (2). Deletion of sprB results in dramatic reduction in motility. Twelve Gld proteins also are required for gliding (3

The typical method for creating targeted contrast agents requires covalent conjugation of separate targeting and fluorophore domains. In this study, we demonstrate that it is possible create tissue-specific near-infrared fluorophores using the inherent chemical structure. Thus, a single compact molecule performs both targeting and imaging. We use this strategy to solve a major problem in head/neck surgery, the identification and preservation of parathyroid and thyroid glands. We synthesized 700-nm and 800-nm halogenated fluorophores that show high uptake in the specific glands after a single intravenous injection of only 0.06 mg kg−1 in a pig. Using a dual-channel near-infrared imaging system, we demonstrate the real-time, high-sensitivity, unambiguous identification of parathyroid and thyroid glands simultaneously in the context of blood and surrounding soft tissue. This novel technology lays the foundation for head/neck surgery performed with increased precision and efficiency, and potentially lowers morbidity, and a general strategy for targeted near-infrared fluorophore development.

Graphical Abstract Renally cleared zwitterionic nanocarriers (H-Dots) are composed of ε-polylysine backbone for charge variations, near-infrared fluorophores for bioimaging, and β-cyclodextrins for potential drug delivery. H-Dots show ideal systemic circulation and rapid distribution and excrete from normal tissue/organ via renal excretion after complete targeting to the tumor site without nonspecific uptake by the immune system.

The conventional method for creating targeted contrast agents is to conjugate separate targeting and fluorophore domains. In this study we report a new strategy based on incorporation of targeting moieties into the non-resonant structure of pentamethine and heptamethine indocyanines. Using the known affinity of phosphonates for bone minerals as a model system, we have synthesized two families of bifunctional molecules that target bone without the need for a traditional bisphosphonate. With peak fluorescence emission at ≈ 700 nm or ≈ 800 nm, these molecules can be used for FLARE dual-channel imaging. Longitudinal FLARE studies in mice demonstrate that phosphonated near-infrared fluorophores remain stable in bone for over 5 weeks, and histological analysis demonstrates incorporation into bone matrix. Taken together, we describe a new strategy for creating ultracompact, targeted, near-infrared fluorophores for various bioimaging applications.

Nerve preservation is an important issue during most surgery because accidental transection or injury results in significant morbidity, including numbness, pain, weakness, or paralysis. Currently, nerves are still identified only by gross appearance and anatomical location during surgery, without intraoperative image guidance. Near-infrared (NIR) fluorescent light, in the wavelength range of 650-900 nm, has the potential to provide high-resolution, high-sensitivity, and real-time avoidance of nerve damage, but only if nerve-specific NIR fluorophores can be developed. In this study, we evaluated a series of Oxazine derivatives to highlight various peripheral nerve structures in small and large animals. Among the targeted fluorophores, Oxazine 4 has peak emission near into the NIR, which provided nerve-targeted signal in the brachial plexus and sciatic nerve for up to 12 h after a single intravenous injection. In addition, recurrent laryngeal nerves were successfully identified and highlighted in real time in swine, which could be preserved during the course of thyroid resection. Although optical properties of these agents are not yet optimal, chemical structure analysis provides a basis for improving these prototype nerve-specific NIR fluorophores even further.

Motility often plays a decisive role in the survival of species. Five systems of motility have been studied in depth: those propelled by bacterial flagella, eukaryotic actin polymerization and the eukaryotic motor proteins myosin, kinesin and dynein. However, many organisms exhibit surprisingly diverse motilities, and advances in genomics, molecular biology and imaging have showed that those motilities have inherently independent mechanisms. This makes defining the breadth of motility nontrivial, because novel motilities may be driven by unknown mechanisms. Here, we classify the known motilities based on the unique classes of movement-producing protein architectures.Based on this criterion, the current total of independent motility systems stands at 18 types. In this perspective, we discuss these modes of motility relative to the latest phylogenetic Tree of Life and propose a history of motility. During the ~4 billion years since the emergence of life, motility arose in Bacteria with flagella and pili, and in Archaea with archaella. Newer modes of motility became possible in Eukarya with changes to the cell envelope. Presence or absence of a peptidoglycan layer, the acquisition of robust membrane dynamics, the enlargement of cells and environmental opportunities likely provided the context for the (co)evolution of novel types of motility. K E Y W O R D S appendage, cytoskeleton, flagella, membrane remodeling, Mollicutes, motor protein, peptidoglycan, three domains | 9Genes to Cells MIYATA eT Al.

Functional near-infrared (NIR) fluorophores have played a major role in the recent advances in bioimaging. However, the optical and physicochemical stabilities of NIR fluorophores in the biological and physiological environment are still a challenge. Especially, the ether linkage on the meso carbon of heptamethine core is fragile when exposed to serum proteins or other amine-rich biomolecules. To solve such a structural limitation, a rigid carbon-carbon bond was installed onto the framework of ether-linked NIR fluorophores through the Suzuki coupling. The robust fluorophores replaced as ZW800-1C and ZW800-3C displayed enhanced optical and chemical stability in various solvents and a 100% warm serum environment (> 99%, 24 h). The biodistribution and clearance of C-C coupled ZW800 compounds were almost identical to the previously developed oxygen-substituted ZW800 compounds. When conjugated with a small molecule ligand, ZW800-1C maintained the identical stable form in warm serum (>98%, 24 h), while ZW800-1A hydrolyzed quickly after 4 h incubation (34%, 24 h).