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Rotaxane
In chemistry, a rotaxane () is a mechanically interlocked molecular architecture consisting of a dumbbell-shaped molecule which is threaded through a macrocycle (see graphical representation). The two components of a rotaxane are kinetically trapped since the ends of the dumbbell (often called ''stoppers'') are larger than the internal diameter of the ring and prevent dissociation (unthreading) of the components since this would require significant distortion of the covalent bonds. Much of the research concerning rotaxanes and other mechanically interlocked molecular architectures, such as catenanes, has been focused on their efficient synthesis or their utilization as artificial molecular machines. However, examples of rotaxane substructure have been found in naturally occurring peptides, including: cystine knot peptides, cyclotides or lasso-peptides such as microcin J25. Synthesis The earliest reported synthesis of a rotaxane in 1967 relied on the statistical probabili ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotaxane Cartoon
In chemistry, a rotaxane () is a mechanically interlocked molecular architectures, mechanically interlocked molecular architecture consisting of a dumbbell-shaped molecule which is threaded through a macrocycle (see graphical representation). The two components of a rotaxane are kinetically trapped since the ends of the dumbbell (often called ''stoppers'') are larger than the internal diameter of the ring and prevent dissociation (chemistry), dissociation (unthreading) of the components since this would require significant distortion of the covalent bonds. Much of the research concerning rotaxanes and other mechanically interlocked molecular architectures, such as catenanes, has been focused on their efficient Chemical synthesis, synthesis or their utilization as artificial molecular machines. However, examples of rotaxane substructure have been found in naturally occurring peptides, including: cystine knot peptides, cyclotides or lasso-peptides such as microcin J25. Synthesis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotaxane Crystal Structure EurJOrgChem Page2565 Year1998
In chemistry, a rotaxane () is a mechanically interlocked molecular architecture consisting of a dumbbell-shaped molecule which is threaded through a macrocycle (see graphical representation). The two components of a rotaxane are kinetically trapped since the ends of the dumbbell (often called ''stoppers'') are larger than the internal diameter of the ring and prevent dissociation (unthreading) of the components since this would require significant distortion of the covalent bonds. Much of the research concerning rotaxanes and other mechanically interlocked molecular architectures, such as catenanes, has been focused on their efficient synthesis or their utilization as artificial molecular machines. However, examples of rotaxane substructure have been found in naturally occurring peptides, including: cystine knot peptides, cyclotides or lasso-peptides such as microcin J25. Synthesis The earliest reported synthesis of a rotaxane in 1967 relied on the statistical probability t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotaxane Crystal Structure ChemComm Page493 2001 Commons
In chemistry, a rotaxane () is a mechanically interlocked molecular architecture consisting of a dumbbell-shaped molecule which is threaded through a macrocycle (see graphical representation). The two components of a rotaxane are kinetically trapped since the ends of the dumbbell (often called ''stoppers'') are larger than the internal diameter of the ring and prevent dissociation (unthreading) of the components since this would require significant distortion of the covalent bonds. Much of the research concerning rotaxanes and other mechanically interlocked molecular architectures, such as catenanes, has been focused on their efficient synthesis or their utilization as artificial molecular machines. However, examples of rotaxane substructure have been found in naturally occurring peptides, including: cystine knot peptides, cyclotides or lasso-peptides such as microcin J25. Synthesis The earliest reported synthesis of a rotaxane in 1967 relied on the statistical probability t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanically Interlocked Molecular Architectures
In chemistry, mechanically-interlocked molecular architectures (MIMAs) are molecules that are connected as a consequence of their topology. This connection of molecules is analogous to keys on a keychain loop. The keys are not directly connected to the keychain loop but they cannot be separated without breaking the loop. On the molecular level, the interlocked molecules cannot be separated without the breaking of the covalent bonds that comprise the conjoined molecules; this is referred to as a mechanical bond. Examples of mechanically interlocked molecular architectures include catenanes, rotaxanes, molecular knots, and molecular Borromean rings. Work in this area was recognized with the 2016 Nobel Prize in Chemistry to Bernard L. Feringa, Jean-Pierre Sauvage, and J. Fraser Stoddart. The synthesis of such entangled architectures has been made efficient by combining supramolecular chemistry with traditional covalent synthesis, however mechanically interlocked molecular architectu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Machine
A molecular machine, nanite, or nanomachine is a molecular component that produces quasi-mechanical movements (output) in response to specific stimuli (input). In cellular biology, macromolecular machines frequently perform tasks essential for life, such as DNA replication and ATP synthesis. The expression is often more generally applied to molecules that simply mimic functions that occur at the macroscopic level. The term is also common in nanotechnology where a number of highly complex molecular machines have been proposed that are aimed at the goal of constructing a molecular assembler. For the last several decades, chemists and physicists alike have attempted, with varying degrees of success, to miniaturize machines found in the macroscopic world. Molecular machines are at the forefront of cellular biology research. The 2016 Nobel Prize in Chemistry was awarded to Jean-Pierre Sauvage, Sir J. Fraser Stoddart, and Bernard L. Feringa for the design and synthesis of molecular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Switch
A molecular switch is a molecule that can be reversibly shifted between two or more stable states. The molecules may be shifted between the states in response to environmental stimuli, such as changes in pH, light, temperature, an electric current, microenvironment, or in the presence of ions and other ligands. In some cases, a combination of stimuli is required. The oldest forms of synthetic molecular switches are pH indicators, which display distinct colors as a function of pH. Currently synthetic molecular switches are of interest in the field of nanotechnology for application in molecular computers or responsive drug delivery systems. Molecular switches are also important in biology because many biological functions are based on it, for instance allosteric regulation and vision. They are also one of the simplest examples of molecular machines. Biological molecular switches In cellular biology, proteins act as intracellular signaling molecules by activating another protein i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macrocycle
Macrocycles are often described as molecules and ions containing a ring of twelve or more atoms. Classical examples include the crown ethers, calixarenes, porphyrins, and cyclodextrins. Macrocycles describe a large, mature area of chemistry. Synthesis The formation of macrocycles by ring-closure is called macrocylization. Pioneering work was reported for studies on terpenoid macrocycles. The central challenge to macrocyclization is that ring-closing reactions do not favor the formation of large rings. Instead, small rings or polymers tend to form. This kinetic problem can be addressed by using high-dilution reactions, whereby intramolecular processes are favored relative to polymerizations. Some macrocyclizations are favored using template reactions. Templates are ions, molecules, surfaces etc. that bind and pre-organize compounds, guiding them toward formation of a particular ring size. The crown ethers are often generated in the presence of an alkali metal cation, whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Electronics
Molecular electronics is the study and application of molecular building blocks for the fabrication of electronic components. It is an interdisciplinary area that spans physics, chemistry, and materials science. The unifying feature is use of molecular building blocks to fabricate electronic components. Due to the prospect of size reduction in electronics offered by molecular-level control of properties, molecular electronics has generated much excitement. It provides a potential means to extend Moore's Law beyond the foreseen limits of small-scale conventional silicon integrated circuits. Molecular scale electronics Molecular scale electronics, also called single-molecule electronics, is a branch of nanotechnology that uses single molecules, or nanoscale collections of single molecules, as electronic components. Because single molecules constitute the smallest stable structures possible, this miniaturization is the ultimate goal for shrinking electrical circuits. Convention ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catenane
In macromolecular chemistry, a catenane () is a mechanically interlocked molecular architecture consisting of two or more interlocked macrocycles, i.e. a molecule containing two or more intertwined rings. The interlocked rings cannot be separated without breaking the covalent bonds of the macrocycles. They are conceptually related to other mechanically interlocked molecular architectures, such as rotaxanes, molecular knots or molecular Borromean rings. Recently the terminology "mechanical bond" has been coined that describes the connection between the macrocycles of a catenane. Catenanes have been synthesised in two different ways: statistical synthesis and template-directed synthesis. Synthesis There are two primary approaches to the organic synthesis of catenanes. The first is to simply perform a ring-closing reaction with the hope that some of the rings will form around other rings giving the desired catenane product. This so-called "statistical approach" led to the fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Motor
Molecular motors are natural (biological) or artificial molecular machines that are the essential agents of movement in living organisms. In general terms, a motor is a device that consumes energy in one form and converts it into motion or mechanical work; for example, many protein-based molecular motors harness the chemical free energy released by the hydrolysis of ATP in order to perform mechanical work. In terms of energetic efficiency, this type of motor can be superior to currently available man-made motors. One important difference between molecular motors and macroscopic motors is that molecular motors operate in the thermal bath, an environment in which the fluctuations due to thermal noise are significant. Examples Some examples of biologically important molecular motors: * Cytoskeletal motors ** Myosins are responsible for muscle contraction, intracellular cargo transport, and producing cellular tension. ** Kinesin moves cargo inside cells away from the nucleus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Shuttle
A molecular shuttle in supramolecular chemistry is a special type of molecular machine capable of shuttling molecules or ions from one location to another. This field is of relevance to nanotechnology in its quest for nanoscale electronic components and also to biology where many biochemical functions are based on molecular shuttles. Academic interest also exists for synthetic molecular shuttles, the first prototype reported in 1991 based on a rotaxane. This device is based on a molecular thread composed of an ethyleneglycol chain interrupted by two arene groups acting as so-called stations. The terminal units (or stoppers) on this wire are bulky triisopropylsilyl groups. The bead is a tetracationic cyclophane based on two bipyridine groups and two para-phenylene groups. The bead is locked to one of the stations by pi-pi interactions but since the activation energy for migration from one station to the other station is only 13 kcal/ mol (54 kJ/mol) the bead shuttles between the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophobic Effect
The hydrophobic effect is the observed tendency of nonpolar substances to aggregate in an aqueous solution and exclude water molecules. The word hydrophobic literally means "water-fearing", and it describes the segregation of water and nonpolar substances, which maximizes hydrogen bonding between molecules of water and minimizes the area of contact between water and nonpolar molecules. In terms of thermodynamics, the hydrophobic effect is the free energy change of water surrounding a solute. A positive free energy change of the surrounding solvent indicates hydrophobicity, whereas a negative free energy change implies hydrophilicity. The hydrophobic effect is responsible for the separation of a mixture of oil and water into its two components. It is also responsible for effects related to biology, including: cell membrane and vesicle formation, protein folding, insertion of membrane proteins into the nonpolar lipid environment and protein-small molecule associations. Hence the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
