High 49-fold

Because of the double helical nature of DNA molecules, their size can be represented in terms of the numbers of nucleotide base pairs they contain. For example, the E. coli chromosome consists of 4.64 X 10 base pairs (abbreviated bp) or 4.64 X 10 kilobase pairs (kbp). DNA is a threadlike molecule. The diameter of the DNA double helix is only 2 nm, but the length of the DNA molecule forming the E. coli chromosome is over 1.6 X 10 nm (1.6 mm). Because the long dimension of an E. coli cell is only 2000 nm (0.002 mm), its chromosome must be highly folded. Because of their long, threadlike nature, DNA molecules are easily sheared into shorter fragments during isolation procedures, and it is difficult to obtain intact chromosomes even from the simple cells of prokaryotes. 

If the two representations are equivalent then Eqs. (3.79) and (3.80) describe how A s and B s must be transformed in terms of a s and /Ts. (These identities are performed explicitly by Sanchez and Di Marzio, [49]. Frank and Tosi [105] further show that if a s and /Ts are chosen to satisfy detailed balance conditions, that is equilibrium behaviour, then the occupation numbers of the two representations are only equivalent if the nv s are in an equilibrium distribution within each stage. This is likely to be true if there is a high fold free energy barrier at the end of each stem deposition, and thus will probably be a good representation for most polymers. In particular, the rate constant for the deposition of the first stem, A0 must contain the high fold free energy term, i.e. ... 

Let us note in addition that the layered sulfides M0S2 and WS2 have been found to form nanotubes and other fullerene-type structures, on account of their highly folded and distorted nature that favors the formation of rag and tubular structures. Such materials have been synthesized by a variety of methods [78] and exhibit morphologies, which were described as inorganic fiillerenes (IF), single sheets, folded sheets, nanocrystals, and nested IFs (also known as onion crystals or Russian dolls ). 

The particle has a head, within which the viral DNA is folded, and a long, fairly complex tail, at the end of which is a series of tail fibers. During the attachment process, the vims particles first attach to the cells by means of the tail fibers. These tail fibers then contract, and the core of the tail makes contact with the cell envelope of the bacterium. The action of a lysozyme-like enzyme results in the formation of a small hole. The tail sheath contracts and the DNA of the vims passes into the cell through a hole in the tip of the tail, the majority of the coat protein remaining outside. The DNA of T4 has a total length of about 50 /xm, whereas the dimensions of the head of the T4 particle are 0.095 Am by 0.065 fim. This means that the DNA must be highly folded and packed very tightly within the head. 

As we noted, the DNA of T4 has a total length about 650 times longer than the dimension of the head. This means that the DNA is highly folded and packed very tightly within the head. 

The newly synthesized cuticle is highly folded and convoluted and thus allows rapid growth after the moult. Certain stages of some parasitic nematodes retain the old cuticle as a protective sheath. 

Some of the chains, when in contact with the shish, will stretch almost completely. However, these highly stretched chains are not dominant compared to the highly folded bundles that form crystalline kebabs around the shish. Also, none of the highly stretched chains formed a structure with part of it stretched and attached to the shish and part of it in folded crystalline lamella. The formation of kebabs in these simulations is clearly growth of lamellae, nucleated on the shish. 

A model of lamellae formation In stretched networks is proposed. Approximately one-half of the chains do not fold. Formation of such lamellae Is accompanied by declining stress. Highly folded systems (high crystallinity), however, can cause a stress Increase. In the calculations crosslinks are assigned to their most probable positions through the use of a characteristic vector. A contingent of amorphous chains Is also Included. The calculations suggest that the concept of fibrillar-lamellar transformations may be unnecessary to explain observed stress-temperature profiles In some cases. 

For the model in Figure 1, y = 1/2, f 1/2, and = 1/3. We can imagine more highly folded models. For example, if half the crystalline chains fold twice and the other half three times, the value of t, is 1/7. The greater the number of folds, the smaller the value of . Since the force at equilibrium is... 

In plants, the photosynthesis reaction takes place in specialized organelles termed chloroplasts. The chloroplasts are bounded in a two-membrane envelope with an additional third internal membrane called thylakoid membrane. This thylakoid membrane is a highly folded structure, which encloses a distinct compartment called thylakoid lumen. The chlorophyll found in chloroplasts is bound to the protein in the thylakoid membrane. The major photosensitive molecules in plants are the chlorophylls chlorophyll a and chlorophyll b. They are coupled through electron transfer chains to other molecules that act as electron carriers. Structures of chlorophyll a, chlorophyll b, and pheophytin a are shown in Figure 7.9. 

Three macrobicycles 40b (216), 40h (212), and 40k (211) were characterized by X-ray crystallography. Fig. 31 displays the structure of 40h. The compounds adopt a highly folded conformation, reminiscent of calixarenes (23) and related Schiff-base macrocycles (181). 

The basic chromophore in 4a,4b-dihydrophenanthrenes is a highly folded fully conjugated hexa-ene bridged by the central two atom unit of carbon atoms 4a and 4b (7 a). This bridge acts both as a poly alkyl substituent and also as a skeletal constraint. 

In tomographic reconstructions of fixed sporozoites, a single, highly folded inner membrane (Fig. 2), or multiple internal subcompartments (see Figs. 12-15, Keithly et al. 2005), were visualized within the organelle. As mentioned before, the infoldings of the IM appeared to lack tubular crista... 

Albumins and globulins are highly folded compact molecules. 

Cells of mycoplasmas sometimes grow as filaments but are often spherical and as small as 0.3 micrometer (pm) in diameter. Their outer surface consists of a thin cell membrane about 8 nanometers (nm) thick. This membrane encloses the cytoplasm, a fluid material containing many dissolved substances as well as sub-microscopic particles. At the center of each cell is a single, highly folded molecule of DNA, which constitutes the bacterial chromosome. Besides the DNA there may be, in a small spherical mycoplasma, about 1000 particles 20 nm in diameter, the ribosomes. These ribosomes are the centers of protein synthesis. Included in the cytoplasm are many different kinds of... 

Each nucleotide pair contributes 0.34 nm to the length of the DNA molecule thus, the total length of DNA of an E. coli chromosome is 1.4 mm. This is about 700 times the length of the cell which contains it. Clearly, the molecules of DNA are highly folded, a fact that accounts for their appearance in the electron microscope as dense aggregates called nucleoids, which occupy about one-fifth of the cell volume (Fig. 1-4). 

Cys residues spaced i, i + 3 apart have been covalently linked to obtain cyclic peptides which fold into a 310-helix. Balaram et al.[159l synthesized Boc-c[-Cys-Pro-Aib-Cys-]-NHMe, wherein a disulfide bond links the two Cys residues. Pro and Aib residues were used to restrict conformational flexibility. NMR and X-ray diffraction studies revealed a highly folded, compact formation of an incipient 3i0-helix, with the S—S bridge lying approximately parallel to the helix axis. 

Mitochondria are intracellular centers for aerobic metabolism. They are cell organelles that are identified by well-defined structural and biochemical properties. In morphological terms, mitochondria are relatively large particles that are characterized by the presence of two membranes, a smooth outer membrane that is permeable to most important metabolites and an inner membrane that has unique transport properties. The inner membrane is highly folded, which serves to increase its surface area. Figure E10.1, which shows the structure of a typical mitochondrion, divides the organelle into four major components inner membrane, outer membrane, intermembrane space, and the matrix. These regions are associated with different and... 

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