Ultrafast Heme Dynamics of Ferric Cytochrome c in Different Environments: Electronic,Vibrational, and Conformational Relaxation

The excited‐state dynamics of ferric cytochrome c (Cyt c), an important electron‐transfer heme protein, in acidic to alkaline medium and in its unfolded form are investigated by using femtosecond pump–probe spectroscopy, exciting the heme and Tryptophan (Trp) to understand the electronic, vibrational, and conformational relaxation of the heme. At 390 nm excitation, the electronic relaxation of heme is found to be ≈150 fs at different pH values, increasing to 480 fs in the unfolded form. Multistep vibrational relaxation dynamics of the heme, including fast and slow processes, are observed at pH 7. However, in the unfolded form and at pH 2 and 11, fast phases of vibrational relaxation dominate, revealing the energy dissipation occurring through the covalent bond interaction between the heme and the nearest amino acids. A significant shortening of the excited‐state lifetime of Trp is observed at various pH values at 280 nm excitation due to resonance energy transfer to the heme. The longer time constant (25 ps) observed in the unfolded form is attributed to a complete global conformational relaxation of Cyt c.     

Carbohydrate‐Based Nanocarriers Exhibiting Specific Cell Targeting with Minimum Influence from the Protein Corona

Whenever nanoparticles encounter biological fluids like blood, proteins adsorb on their surface and form a so‐called protein corona. Although its importance is widely accepted, information on the influence of surface functionalization of nanocarriers on the protein corona is still sparse, especially concerning how the functionalization of PEGylated nanocarriers with targeting agents will affect protein corona formation and how the protein corona may in turn influence the targeting effect. Herein, hydroxyethyl starch nanocarriers (HES‐NCs) were prepared, PEGylated, and modified on the outer PEG layer with mannose to target dendritic cells (DCs). Their interaction with human plasma was then studied. Low overall protein adsorption with a distinct protein pattern and high specific affinity for DC binding were observed, thus indicating an efficient combination of “stealth” and targeting behavior.     

Protein Patterns and Oscillations on Lipid Monolayers and in Microdroplets

The Min proteins from E.coli position the bacterial cell‐division machinery through pole‐to‐pole oscillations. In vitro, Min protein self‐organization can be reconstituted in the presence of a lipid membrane as a catalytic surface. However, Min dynamics have so far not been reconstituted in fully membrane‐enclosed volumes. Microdroplets interfaced by lipid monolayers were employed as a simple 3D mimic of cellular compartments to reconstitute Min protein oscillations. We demonstrate that lipid monolayers are sufficient to fulfil the catalytic role of the membrane and thus represent a facile platform to investigate Min protein regulated dynamics of the cell‐division protein FtsZ‐mts. In particular, we show that droplet containers reveal distinct Min oscillation modes, and reveal a dependence of FtsZ‐mts structures on compartment size. Finally, co‐reconstitution of Min proteins and FtsZ‐mts in droplets yields antagonistic localization, thus demonstrating that droplets indeed support the analysis of complex bacterial self‐organization in confined volumes.     

Bioelectrocatalysis of Dopamine Using Adsorbed Tyrosinase on Single-Walled Carbon Nanotubes

Abstract

A wealth of information on the reactions of redox-active sites in proteins can be obtained by voltammetric studies in which the protein sample is arranged as a layer on a suitable electrode surface. Here, we describe a method for the performance of a tyrosinase/single-walled carbon nanotubes/glassy carbon (Tyr/SWCNTs/GC) electrode, prepared by the modification of GC electrode surface by SWCNTs and adsorption of tyrosinase on the SWCNT surfaces. SWCNTs were studied with the help of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The dimensions of SWCNTs make them ideal candidates for the adsorption of proteins. The copper-containing enzyme, tyrosinase, exhibited an electrical contact with the electrode, because of the structural alignment of the enzyme on the SWCNT surfaces. The apparent Michaelis–Menten constant (K _m) for dopamine (DA) and the stability of the enzyme electrode were estimated. This method could be suitable for applications to nanofabricated devices.     

Phosphatidylcholine‐Coated Iron Oxide Nanomicelles for In Vivo Prolonged Circulation Time with an Antibiofouling Protein Corona

We report the synthesis of micellar phosphatidylcholine‐coated superparamagnetic iron oxide nanoparticles as a new long circulation contrast agents for magnetic resonance imaging. Oleic acid‐coated Fe₃O₄ nanoparticles were first prepared through thermal degradation and then encapsulated into small clusters with a phosphatidylcholine coating to obtain hydrophilic nanomicelles. A thorough characterization confirmed the chemical nature of the coating and the excellent colloidal stability of these nanomicelles in aqueous media. Magnetization and relaxivity properties proved their suitability as magnetic resonance imaging (MRI) contrast agent and in vitro cell viability data showed low toxicity. Vascular lifetime and elimination kinetics in the liver were assessed by blood relaxometry and by in vivo MRI in rats and compared with “control” particles prepared with a polyethylene glycol derivative. These micellar particles had a lifetime in blood of more than 10 h, much longer than the control nanoparticles (≈2 h), which is remarkable considering that the coating molecule is a small biocompatible zwitterionic phospholipid. The protein corona was characterized after incubation with rat serum at different times by high‐throughput proteomics, showing a higher proportion of bound apolipoproteins and other dysopsonins for the phosphatidylcholine particles. The antibiofouling properties of this corona and its resistance to the adsorption of proteins corroborate the observed enhanced stability and prolonged systemic circulation.     

Controlling Radical Formation in the Photoactive Yellow Protein Chromophore

To understand how photoactive proteins function, it is necessary to understand the photoresponse of the chromophore. Photoactive yellow protein (PYP) is a prototypical signaling protein. Blue light triggers trans–cis isomerization of the chromophore covalently bound within PYP as the first step in a photocycle that results in the host bacterium moving away from potentially harmful light. At higher energies, photoabsorption has the potential to create radicals and free electrons; however, this process is largely unexplored. Here, we use photoelectron spectroscopy and quantum chemistry calculations to show that the molecular structure and conformation of the isolated PYP chromophore can be exploited to control the competition between trans–cis isomerization and radical formation. We also find evidence to suggest that one of the roles of the protein is to impede radical formation in PYP by preventing torsional motion in the electronic ground state of the chromophore.     

Isoprene Polymerization on Iron Nanoparticles Confined in Carbon Nanotubes

The confinement of air‐protected metallic magnetic nanoparticles in the inner cavity of carbon nanotubes (CNTs) should offer an interesting perspective for biomedical applications or for controlling CNT alignment in composites. Because the direct confinement of polymer‐precoated nanoparticles in CNTs could be restricted by diffusion limitations, we developed a process based on: 1) the confinement of iron nanoparticles surface‐modified with an iron polymerization catalyst in the cavity of CNTs and 2) the polymerization of isoprene on the confined nanoparticles. The resulting material consists in CNT‐confined iron nanoparticles coated with a polyisoprene air barrier. This approach constitutes a proof of concept for the development of smart materials for use in medicine or composites.     

Polymer Nanoparticles Based on Pyrene‐Functionalized Poly(acrylic acid) for Controlled Release under Photo and pH Stimulation

A novel photo and pH‐responsive amphiphilic pyrene‐functionalized polymer is synthesized by the esterification reaction between poly(acryloyl chloride) and pyrenemethanol and subsequent hydrolysis of the unreacted acylchloride groups. This random copolymer consists of hydrophobic pyrene‐containing acrylate units and hydrophilic acrylic acid units, which can self‐assemble into nanoparticles in water. Under UV irradiation, the nanoparticles can be disrupted with decreasing particle number resulted from the photolysis of pyrenylmethyl esters, where the hydrophobic segments are converted to hydrophilic acrylic acids; at low pH, the acrylic acid segments are protonated and collapsed, thus the nanoparticles will be shrunk and aggregated; at high pH, the nanoparticles change to fractal structures owing to the aggregation of partially dissociated nanoparticles and the subsequent structural reorganization of the clusters. The controlled release of Nile Red from the nanoparticles stimulated by photo and pH separately and synergistically is demonstrated. The nanoparticles self‐assembled from the dual‐stimuli‐sensitive polymer can be used as a new nanocarrier and find their applications in delivery system.

     

Nanoparticle‐Assisted Alignment of Carbon Nanotubes on DNA Origami

Aligning carbon nanotubes (CNTs) is a key challenge for fabricating CNT‐based electronic devices. Herein, we report a spherical nucleic acid (SNA) mediated approach for the highly precise alignment of CNTs at prescribed sites on DNA origami. We find that the cooperative DNA hybridization occurring at the interface of SNA and DNA‐coated CNTs leads to an approximately five‐fold improvement of the positioning efficiency. By combining this with the intrinsic positioning addressability of DNA origami, CNTs can be aligned in parallel with an extremely small angular variation of within 10°. Moreover, we demonstrate that the parallel alignment of CNTs prevents incorrect logic functionality originating from stray conducting paths formed by misaligned CNTs. This SNA‐mediated method thus holds great potential for fabricating scalable CNT arrays for nanoelectronics.     

碳纳米管与生物分子的相互作用*

碳纳米管是一种具有特殊结构和性质的新型一维纳米材料,在生物学和临床医学上已有许多应用研究。大量研究表明,碳纳米管在药物载体、医学成像、疾病检测等方面有广泛的应用前景,碳纳米管与生物分子相互作用的具体机理和形式也成为目前研究的热门方向。本文总结了近几年来碳纳米管与氨基酸、多肽、蛋白质、酶、DNA等多种生物分子之间的相互作用,并对碳纳米管的生物学效应进行了相关综述。     

Polymer Nanoparticles for Controlled Release Stimulated by Visible Light and pH

Polymer nanoparticles are prepared by self‐assembly of visible light and pH sensitive perylene‐functionalized copolymers which are synthesized by quaternization between 1‐(bromomethyl)perylene and the dimethylaminoethyl units of poly(dimethylaminoethyl methacrylate) (PDMAEMA). The perylene‐containing polymethacrylate segments afford the system visible light responsiveness and the unquaternized PDMAEMA segments afford the system pH responsiveness. The self‐assembled nanoparticles exhibit a unique dual stimuli response. They can be photocleaved under visible light irradiation, shrunken to smaller nanoparticles at high pH, and swollen at low pH. The structural change endows the nanoparticle with great potential as a sensitive nanocarrier for controlled release of Nile Red and lysozyme under this stimulation. The visible light responsiveness and synergistic effect on the release of loaded molecules with the dual stimulation may obviate the need for harsh conditions such as UV light or extreme pH stimulation, rendering the system more applicable under mild conditions.

     

氮掺杂多壁纳米碳管的合成和定量表征

 采用化学气相沉积法制备了 N 掺杂多壁纳米碳管, 并运用透射电子显微镜、N2 物理吸附、热重-差示扫描量热、程序升温氧化和 X 射线光电子能谱等手段对样品进行了表征. 结果表明, 纯化处理的纳米碳管表面 N 含量为 4.2%, 其中包括吡啶、己内酰胺、氧化吡啶、吡啶酮和吡咯等含氮官能团. 研究了各种含氮官能团燃烧的动力学行为. N 原子掺杂进入碳管的石墨结构中, 提高了表面碱性, 有可能用于催化与能源转化领域. 另外, 本文提供了一种可用于场发射器件的杯状闭合结构纳米碳合成方法.     

Polymer Micro‐ and Nanocapsules as Biological Carriers with Multifunctional Properties

The design and development of multifunctional polymer capsules with controlled chemical composition and physical properties has been the focus of academic and industrial research in recent years. Especially in the biomedical field, the formulation of novel polymer‐based encapsulation systems for the early‐stage disease diagnostic and effective delivery of bioactive agents represent one of the most rapidly advancing areas of science. The stimuli‐responsive release of cargo molecules from the carrier gains remarkable attention for in vitro and in vivo delivery of contrast agents, genes, and pharmaceutics. In this Review, the current status and the challenges of different polymer‐based micro‐ and nanocapsule formulations are considered, emphasizing on their potential biological application as carriers for specific drug targeting and controlled release upon applying of external stimulus.     

Pay Attention to Biological Nanoparticles when Studying the Protein Corona on Nanomedicines

The protein corona of nanoparticles has in recent years received considerable attention, and even been postulated to be the missing link in the translation of nanomedicines from benchtop to bedside. We highlight the different types of biological nanoparticles present in blood that need to be considered in the protein corona research field. We map their size, density, and plasma concentrations, and use this information to stress potential challenges related to the isolation of nanomedicines—with a particular focus on liposomes—when using the traditional isolation methods that separate according to size and density.     

Dynamics of the Size Distribution of CdTe Quantum Dot Ensembles during Growth in Liquid and Crystalline Phases

We recently reported that the growth rate of colloidal CdTe nanoparticles decreases by orders of magnitude when the particles undergo a phase transition from liquid to crystal. The dynamics of nanoparticle growth are dominated by this factor rather than the size dependence of the chemical potential. Herein we discuss how the phase transition affects the size distribution and photoluminescence quantum efficiency of the nanoparticles. We suggest that the absorption linewidth is a better monitor of size distribution than the photoluminescence linewidth because the photoluminescence quantum efficiency, which affects the latter via energy transfer, varies substantially with reaction time. We find that the size distribution broadens in the early stages of growth possibly because of inhomogeneities in the phase transition radius or because particles nucleated at later times coalesce with nanocrystals. The quantum efficiency is enhanced when tellurium is depleted in the reaction solution, giving a cadmium‐enriched surface. Batches with high initial tellurium and cadmium concentrations show a substantial amount of delayed nucleation, lower quantum efficiency and some anisotropic growth.