Encoding coil

In most four-helix bundle structures, including those shown in Figure 3.7, the a helices are packed against each other according to the "ridges in grooves" model discussed later in this chapter. However, there are also examples where coiled-coil dimers packed by the "knobs in holes" model participate in four-helix bundle structures. A particularly simple illustrative example is the Rop protein, a small RNA-binding protein that is encoded by certain plasmids and is involved in plasmid replication. The monomeric sub unit of Rop is a polypeptide chain of 63 amino acids built up from two... 

Many enveloped viruses share a common mechanism of fusion, mediated by a virus-encoded glycoprotein that contains heptad repeats in its extraceUnlar domain. Dnring the fnsion process, these domains rearrange to form highly structured and thermodynamically stable coiled-coils. Viruses encoding fusion proteins that have these domains inclnde members of the paramyxovirus family (e.g., respiratory syncytial virus, metapneumovirus, and measles virus), ebola virus, influenza, and members of the retroviridae (e.g., human T cell lenkemia virus type-1 and human immunodeficiency virus type-1, HlV-1). Peptide inhibitors of fusion that disrupt the... 

In order to use Eqs. (2.6.1) and (2.6.2) to estimate the sensitivity gain obtained by remote detection, knowledge of the relative sensitivity of the detector and the encoding circuit, A, is required. Here we discuss the sensitivity of an rf coil detector as an example, because all the experiments presented in this text use inductive detection at high field. The signal-to-noise ratio of inductive NMR detection can be approximated by the following simplified equation [12] ... 

Most of the commercially available NMR imaging probes have an accessible clear bore above and below the coil, which can be used for remote signal encoding. A detection-only probe can be inserted from the top into the bore of the magnet in such a way that the detection coil sits immediately above the imaging coil [Figure 2.6.5 (c)]. Similarly, an rf probe with a narrow body can be built that can be inserted into the... 

Fig. 2.6.7 General principle of time-of-flight flow detection, (a) Schematic of a set-up for TOF experiments. An object of interest is placed inside an environment optimized for encoding (field gradients not shown). As the sensor medium flows out of the analyte object, its magnetization is recorded with a second coil with a smaller volume, which is placed as close to the encoding volume as possible, (b) Generic pulse sequence used for TOF experiments. Encoding along one dimension can be done by inverting the magnetization of a slice...

Fig. 2.6.10 Specialized experimental set-up for microfluidic flow dispersion measurements. Fluid is supplied from the top, flows via a capillary through the microfluidic device to be profiled and exits at the bottom. The whole apparatus is inserted into the bore of a superconducting magnet. Spatial information is encoded by MRI techniques, using rf and imaging gradient coils that surround the microfluidic device. They are symbolized by the hollow cylinder in the figure. After the fluid has exited the device, it is led through a capillary to a microcoil, which is used to read the encoded information in a time-resolved manner. The flow rate is controlled by a laboratory-built flow controller at the outlet [59, 60].

Fig. 5. Pulse sequence for MR detection of vibration using a radiofrequency field gradient. A binomial 1331 radiofrequency pulse (pulse length D, interpulse delay r) is applied in-phase with the mechanical wave. Thus the vibration period 7V is equal to 4(D + r). The number of cycles can be increased to ensure a better frequency selectivity. The constant RF field gradient generated by a dedicated RF coil allows space encoding without using conventional static field gradients (from Ref. 16 with permission from Elsevier).

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