Proton artificial

Figure C3.2.17. Diagram of a liposome-based artificial photosynthetic membrane showing the photocycle that pumps protons into the interior of the liposome and the CFqF j-ATP synthase enzyme. From [55],...

Saccharin was discovered at Johns Hopkins Uni versity in 1879 in the course of research on coal tar derivatives and is the oldest artificial sweetener In spite of Its name which comes from the Latin word for sugar saccharin bears no structural relationship to any sugar Nor is saccharin itself very soluble in wa ter The proton bonded to nitrogen however is fairly acidic and saccharin is normally marketed as its water soluble sodium or calcium salt Its earliest applications were not in weight control but as a... 

With only 90 elements, one might assume that there could be only about 90 different substances possible, but everyday experience shows that there are millions of different substances, such as water, brick, wood, plastics, etc. Indeed, elements can combine with each other, and the complexity of these possible combinations gives rise to the myriad substances found naturally or produced artificially. These combinations of elemental atoms are called compounds. Since atoms of an element can combine with themselves or with those of other elements to form molecules, there is a wide diversity of possible combinations to make all of the known substances, naturally or synthetically. Therefore, atoms are the simplest chemical building blocks. However, to understand atoms, it is necessary to examine the structure of a typical atom or, in other words, to examine the building blocks of the atoms themselves. The building blocks of atoms are called electrons, protons, and neutrons (Figure 46.1). 

Monensin, which is one of the natural antibiotics, selectively transports Na+ across an artificial liquid membrane (organic solvent) from the basic aqueous phase (IN) to the acidic aqueous phase (OUT), driven by the proton gradient8). (Fig. 1, 2)... 

A few elements, among them fluorine and phosphoras, occur naturally with just one isotope, but most elements are isotopic mixtures. For example, element number 22 is titanium (Ti), a light and strong metal used in Jet engines and in artificial human Joints. There are five naturally occurring isotopes of Ti. Each one has 22 protons in its nuclei, but the number of neutrons varies from 24 to 28. In a chemical reaction, all isotopes of an element behave nearly identically. This means that the isotopic composition of an element remains essentially constant. The isotopic composition of Ti (number percentages) is... 

Decarboxylases are one of the members of the enolase superfamily. The most important and interesting point of this class of enzymes is that they are mechanistically diverse and catalyze different overall reactions. However, each enzyme shares a partial reaction in which an active site base abstracts a proton to form a nucleophile. The intermediates are directed to different products in the different active sites of different members. However, some enzymes of this class exhibit catalytic promiscuity in their natural form. ° This fact is considered to be strongly related to the evolution of enzymes. Reflecting the similarity of the essential step of the total reaction, there are some successful examples of artificial-directed evolution of these enzymes to catalyze distinctly different chemical transformation. The changing of decarboxylase to racemase described in Section 2.5 is also one of these examples. 

Artificial radioactive atoms are produced either as a by-product of fission of uranium or plutonium atoms in a nuclear reactor or by bombarding stable atoms with particles, such as neutrons or protons, directed at... 

Second, the resolution achieved in a 2-D experiment, particularly in the carbon domain is nowhere near as good as that in a 1-D spectrum. You might remember that we recommended a typical data matrix size of 2 k (proton) x 256 (carbon). There are two persuasive reasons for limiting the size of the data matrix you acquire - the time taken to acquire it and the shear size of the thing when you have acquired it This data is generally artificially enhanced by linear prediction and zero-filling, but even so, this is at best equivalent to 2 k in the carbon domain. This is in stark contrast to the 32 or even 64 k of data points that a 1-D 13C would typically be acquired into. For this reason, it is quite possible to encounter molecules with carbons that have very close chemical shifts which do not resolve in the 2-D spectra but will resolve in the 1-D spectrum. So the 1-D experiment still has its place. 

However, there are still important reactivity features which have so far been neglected by the reactivity functions, but yet which must be accounted for even at this stage of development if a sensible overall approach is to result. An important case concerns the special position of the hydrogen atom, and its ion, the proton. Its peculiar role in chemistry is reflected particularly in the way that even weakly basic solvents are able to interact with, and stabilize, it to a degree sufficient to render it a common and feasible independent entity in chemical reactions. This is in marked contrast to simple alkyl group ions, such as the methyl cation, whose electronic properties in many respects are very similar to those of the proton. Our current level of model development does not reflect this difference, and so specific allowance must be made artificially for the proton. 

Imura and Suzuki36 have prepared labelled organotin compounds from artificial tin isotopes produced in a cyclotron. The carrier-free tin-113 radioisotope was produced by irradiating indium-115 oxide with 40-MeV protons (equation 33). 

ARTIFICIAL PHYTANYL-CHAINED GLYCOLIPID VESICLE MEMBRANES WITH LOW PROTON PERMEABILITY ARE SUITABLE FOR PROTON PUMP RECONSTITUTION MATRICES... 

In this paper, we will describe one of examples, where artificial archaeal glycolipids are applied to the construction of nano-devices containing energy-conversion membrane proteins, by employing the phytanyl-chained glycolipid we have recently developed, i.e., l,3-di-o-phytanyl-2-o- ((3-D-maltotriosyl) glycerol (Mab (Phyt)2, Fig. 1) [16,17] and natural proton pump, bacteriorhodopsin (BR) derived from purple membranes of the extremely halophilic archaeon Halobacterium salinarium S9 [18],... 

These significant findings form the basis of a set of design principles for the construction of molecular photovoltaic cells and other nanoscale electronic devices in which the control of both the rate and directionality of ET processes is an essential requirement. The successful construction of an artificial light-driven proton pump, based on principles of long-range ET processes illustrates the promise of this approach.1501... 

G. Steinberg-Yfrach, P. A. Liddell, S. C. Hung, A. L Moore, D. Gust, T. A. Moore, Conversion of Light Energy to Proton Potential in Liposomes by Artificial Photosynthetic Reaction Centres , Nature 1997,385,239-241. 

The number of protons is unique to the element but most elements can exist with two or more different numbers of neutrons in their nucleus, giving rise to different isotopes of the same element. Some isotopes are stable, but some (numerically the majority) have nuclei which change spontaneously - that is, they are radioactive. Following the discovery of naturally radioactive isotopes around 1900 (see Section 10.3) it was soon found that many elements could be artificially induced to become radioactive by irradiating with neutrons (activation analysis). This observation led to the development of a precise and sensitive method for chemical analysis. 

NOESY varied from 12 h to 48 h, depending on the ligand concentration (between 500 pM and 2 mM). Occasional ambiguities due to proton overlap among Thr and Met residues were resolved by recording a 3D [13C, HJ-resolved [ H, HJ-NOESY experiment. QUIET-NOESY (Quenching Undesirable Indirect External Trouble in NOESY) experiments [34] were also performed to avoid artificial NOE cross peaks arising from spin diffusion. (Taken from Ref. [4]). 

Francium occurs as a result of the disintegration of actinium. Francium is found in uranium minerals, and can be made artificially by bombarding thorium with protons. It is the most unstable of the first 101 elements. 

Matsson and coworkers have measured the carbon-1 l/carbon-14 kinetic isotope effects for several Menshutkin reactions (equation 35) in an attempt to model the S/v2 transition state for this important class of organic reaction. These isotope effects are unusual because they are based on the artificially-made radioactive carbon-11 isotope. The radioactive carbon-11 isotope is produced in a cyclotron or linear accelerator by bombarding nitrogen-14 atoms with between 18- and 30-MeV protons (equation 36). 

The protons/electrons produced in water oxidation at a photoanode side of a PEC device could be used (on the cathode side) to reduce C02 to alcohols/hydrocarbons (CH4, CH30H, HC00H, etc.). In this way, an artificial leaf (photosynthesis) device could be developed [11]. While nanocarbon materials containing iron or other metal particles show interesting properties in this C02 reduction [106], it is beyond the scope of this chapter to discuss this reaction here. It is worthwhile, however, to mention how nanocarbon materials can be critical elements to design both anode and cathode in advanced PEC solar cells. Nanocarbons have also been successfully used for developing photocatalysts active in the reduction of C02 with water [107]. 

Isotrope, Having the same atomic number (and position in the Periodic Table of Elements) but different masses. The difference is due to extra neutrons in the nucleus. For example hydrogen, one of three isotopes, has an atomic number of 1 and a mass of 1 the naturally occurring deuterium has a mass of 2 because it has an extra neutron in its nucleus the artificially produced tritium has another neutron for a mass of three. All three have one proton and electron and, hence, an atomic number of 1. 

---