ABSTRACT
Manipulating and measuring single-molecule dynamics and reactions in nanofluidics is a rapidly growing field with broad applications in developing new biotechnologies, understanding nanoconfinement effects in vivo, and exploring new phenomena in confinement. In this work, we investigate the kinetics of DNA collapse in nanoslits using single T4-DNA (165.6 kbp) and λ-DNA (48.5 kbp), with particular focus on the measurement of the nucleation and annealing times. Fixing the ethanol concentration at 35% and varying the slit height from 2000 to 31 nm, the nucleation time dramatically decreases from more than 1 hour to a few minutes or less. The increased collapsed rate results from the larger free energy experienced by coiled DNA in confinement relative to compacted DNA. Our results also shed light on other conformational transitions in confinement, such as protein folding.
Subject(s)
DNA, Viral/chemistry , Nanotechnology/methods , Bacteriophage T4/genetics , Kinetics , Surface PropertiesABSTRACT
Exploration of intrachain hydrodynamics of dsDNA within channels has been limited to indirect analysis of global coil dynamics. In this Letter, we isolate hydrodynamic interactions within single molecules of dsDNA confined to slitlike channels by making use of density covariance measurements. We show that the strength of hydrodynamic interactions in DNA is dependent on the intrachain correlation length and that screening by symmetry in slitlike confinement results in a screening length that is proportional channel height. Moreover, we directly show the partial draining nature of the blobs formed by dsDNA in slits and predict under what conditions a dsDNA blob should obey nondraining Zimm behavior.
Subject(s)
DNA/chemistry , Models, Chemical , Benzoxazoles/chemistry , Fluorescent Dyes/chemistry , Hydrodynamics , Intercalating Agents/chemistry , Nucleic Acid Conformation , Quinolinium Compounds/chemistry , ThermodynamicsABSTRACT
We experimentally and numerically study the effects of macromolecular crowding agents on DNA structure when confined to a nanochannel. Curiously, DNA response to crowding is significantly different between bulk phase, nanoslit confinement, and nanotube confinement. Coarse grained Brownian dynamics simulations reproduce trends seen in the experiments and allow us to develop a deeper understanding of the key physics at play in these systems. It is proposed that the occupancy of free volume next to the channel wall by crowders causes an effective reduction in confining dimensions of the channel that initially swells DNA in nanoconfinement.
Subject(s)
DNA/chemistry , DNA/ultrastructure , Macromolecular Substances/chemistry , Models, Chemical , Nanostructures/chemistry , Nanostructures/ultrastructure , Computer Simulation , Materials Testing , Models, Molecular , Molecular Conformation , Particle SizeABSTRACT
Lumps and bumps of the scalp are a common presenting complaint in children and often pose a diagnostic dilemma. These lesions can be difficult to image, with evaluation confounded by their small size. However, accuracy in diagnosis is critical because the diagnostic and therapeutic implications can vary significantly. The clinical examination can be helpful in developing the differential diagnosis and the imaging strategy. Often, however, a single imaging study is insufficient, and the radiologist finds it necessary to image with more than one modality to correctly diagnose a lesion and provide adequate information for the surgeon. Radiography and ultrasonography are often the initial screening diagnostic tests, followed by magnetic resonance (MR) imaging or computed tomography (CT) for more detail. Multidetector thin-section CT and thin-section MR imaging with surface coils are beneficial in the work-up of these small lesions of the head and neck. The use of newer MR imaging sequences such as heavily T2-weighted single-shot turbo spin-echo imaging and diffusion-weighted imaging can improve the characterization of difficult lesions. Familiarity with the variety of new imaging tools and techniques that are available can help characterize pediatric head and neck lesions and guide clinical management.
Subject(s)
Magnetic Resonance Imaging , Scalp Dermatoses/diagnosis , Skull , Tomography, X-Ray Computed , Bone Diseases/congenital , Bone Diseases/diagnosis , Child , Diagnosis, Differential , Humans , Scalp Dermatoses/congenitalABSTRACT
B cell-deficient C57B1/6 (microMT) mice were resistant to Leishmania major after both primary and secondary parasite challenge. However, unlike in wild-type mice, secondary infection in microMT mice was not accompanied by a marked delayed type hypersensitivity-like response, and interferon-gamma (IFN-gamma) levels were approximately half of those in wild-type mice. These results suggest that B cells are involved in IFN-gamma production and the pathology of secondary infection.
