Complex masking with

Fig. 4. Example of output from the seg program (Wootton, 1994). The seg program was run with default parameters on the SWISS-PROT sequence PSPDHUMAN. (A) Tree output format from seg. Lower case sequence on the left is low complexity, whereas the sequence on the right is high complexity. Note that only the regions between residues 13 and 47 and residues 152 and 375 are large enough to contain protein domains. (B) The second output from seg shows the regions of low complexity masked with Xs this sequence is ready for database searching.

After dissolution of the alloy in a mixture of concentrated nitric and hydrochloric acids the iron is masked with triethanolamine in an alkaline medium, and the manganese titrated with standard EDTA solution using thymolphthalexone as indicator. The amount of iron(III) present must not exceed 25 mg per 100 mL of solution, otherwise the colour of the iron(III)-triethanolamine complex is so intense that the colour change of the indicator is obscured. Consequently, the procedure can only be used for samples of ferro-manganese containing more than about 40 per cent manganese. 

Electrochemical Instrumentation. For the Ru complexes, a 1 cm diameter platinum disk brazed onto a brass holder was used as a working electrode. It was masked with ChemGrip (a teflon based epoxy) except for the upper face. Prior to use, it was polished with 1 micron diamond paste (Buehler) and rinsed with water, acetone and methanol. The working electrode for each Os complex was the uppermost platinum layer of a platinum/carbon layered synthetic microstructure (LSM) (Energy Conversion Devices). The LSM consisted of 200 layer pairs of carbon and platinum whose thicknesses were 24.4 and 17.0 A, respectively and where platinum was the outermost layer. The LSM was placed in 1.0 M H2SO4 and cleaned... 

The complexometric method for determination of Ca(II) and Mg(II) is based on two titrations with EDTA in alkaline solution, one where both ions are determined together and the second after one of them has been masked with a specific complexing agent. The effect of interfering heavy metals such as Cu, Fe, Mn or Zn can be avoided by adding cyanide. The AOAC Official Method 964.01 for determination of acid-soluble... 

Figure 11 shows such sigmoid curves for a hypothetical system where curve (a) is drawn for complex ML2 with [HL]org = 10-3 M and Kex = 102. Curves (b), (c) and (d) are drawn for [HL]org = 10-5 M, Ktx = 102 for complexes ML, ML2 and ML3 respectively. Curve (e) represents a complex ML2 for which [HL]org = 10-5 M but Kex = 10"2. The control that can be exercised by change of [HL]org and pH will be obvious and separations will always be possible if values of for two metals are different, for besides the variables mentioned above auxiliary complexing agents may be included in the aqueous phase to mask one or more of the unwanted cations (Section 10.3). Specific examples will be described for only one particular extractant (dithizone) to illustrate the general principle (Section 10.4.4.5). 

Fig. 16 Photocurrent-voltage curve of a solar cell based on complex 26. The cell was equipped with an anti-reflective coating. The conversion efficiency in full AM 1.5 sunlight illumination (100 mW cm-2) is 11.18%. The cell is masked with black plastic to avoid the diffusive light leaving an active cell area of 0.158 cm2...

A somewhat different approach was used by Vincent in phase-switching reactions using pyridyl-labelled substrates and products. The pyridyl-containing tag is here thought of as a masked phase tag, which allows for phase switching with the help of a heavy fluorous copper(ll)-carboxylate complex. Comparison with a non-fluorous system indicated that a problem of release of the strongly coordinating pyridine linker was avoided in the fluorous approach. ... 

Fig. 12.17). The additional mask required for OE is a reversed copy of the STI mask with reduced structure size. RIE then removes the oxide in the exposed areas, stopping on the nitride. After RIE of the oxide and resist removal, the remaining nonplanarity at the periphery of the active areas is easily removed with CMP. The planarity results are excellent (Fig. 12.18), and unlike in the case of dummy insertion, planarity improvement is achieved without a negative impact on performance. The main disadvantage of the technique is the increased process complexity due to the additional lithography and RIE steps. 

A simple and rapid method for the iodometric determination of microgram amounts of chromium(ni) in organic chelates is based on the oxidation of chromium(III) with periodate at pH 3.2, removal of the umeacted periodate by masking with molybdate and subsequent iodometric determination of the liberated iodate . Iodometric titration was also used for determination of the effective isoascorbate (see 2) concentration in fermentation processes . The content of calcium ascorbate can be determined with high sensitivity by complexometric titration with edta, which is superior to iodometry. The purity of /3 -diketonate complexes of Al, Ga, In and Ni was determined by complexometric titration with edta at pH 5.5-3, with RSD < 0.01 for determining 5-30% metal ion. Good analytical results were obtained by a similar procedure for the metal content of 15 lanthanide organic complexes. ... 

Case 1. Lower chelates in aqueous phase (hydroxyl complexes, masking effects, and adducts negligible) Particularly with multivalent metals, an appreciable fraction of the metal ion in the aqueous phase may exist as lower complexes. Thus Rydberg, in studying the extraction of thorium acetylacetonate from water... 

Aluminum is extracted from sea water into chloroform after complexation with pyrocatechol violet and the formation of an ion associate of the aluminum complex with zephiramine (tetradecyldimethylbenzylammonium chloride). With 5 ml of chloroform as much as 94.7% of the aluminum was separated from 110 ml of sea water, i.e. a 20-fold aluminum concentration could easily be achieved. Several ions, such as manganese, iron(II), iron(III), cobalt, nickel, copper, zinc, cadmium, lead, and uranyl also react with pyrocatechol violet and to some extent are extracted together with aluminum. However, the interferences of these ions and other metal ions present in sea water could be eliminated by masking with sodium diethyl-dithiocarbamate and 8-hydroxyquinaldine. In presence of these agents all the above metal ions except aluminum were extracted into chloroform51). 

Nucleophilic complex bases with good nucleophiles as activating agents. In this group, nucleophilic properties are masked but they do not completely disappear. 

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