Null line

The essentials of the major pathway to Ins P6 in yeast nuclei can be summarized as follows Ins — Ptdlns, catalyzed by Ptdlns synthase Ptdlns —>PtdIns(4,5) P2, catalyzed sequentially by two specific kinases PtdIns(4,5)P2—>Ins (1,4,5)P3, catalyzed by a Ptdlns-specific phospholipase C Ins(l,4,5)P3—>—> Ins(l,3,4,5,6)P5, catalyzed by an Ins(l,4,5)P3 3-/6-kinase Ins(l,3,4,5,6)P5 —> Ins P6, catalyzed by an Ins(l,3,4,5,6)P5 2-kinase. This is now viewed as the canonical PLC-dependent pathway. Recent genetics studies have shown that this pathway is also critical to Ins P6 synthesis in Drosophila and rat cells (Fujii and York, 2004 Seeds et al., 2004). In contrast, the sole genetic evidence in any organism for a PLC-independent pathway like that described above in Dictyostelium and Spirodela, one that proceeds solely via soluble Ins phosphates, consists of one elegant study using Dictyostelium (Drayer et al., 1994). In this study the presence and levels of the whole series of Ins phosphates typical of a wild-type Dictyostelium, including Ins(l,4,5)P3 and Ins P6, where shown to be essentially identical in a PLC-null line. Thus some pathway to Ins(l,4,5)P3 and Ins P6 independent of PLC must exist in this organism. 

Kramers and Pauli have endeavoured to treat the band spectra of molecules whose electronic angular momentum has a direction fixed in the molecule but is otherwise unrestricted, and to explain the absence of the null line, by applying to molecules the model of the top with an enclosed fly-wheel. 

The infra-red spectra of the halogen hydrides are of the type described here but without null branches.1 These spectra consist of individual double bands, i.e. an approximately equidistant succession of lines, which are symmetrically situated with respect to a gap. In this gap we have to imagine the null line mentioned in 19. A doubling-back of the one branch is not observed in this case. 

A beautiful example of a band system is provided by the violet cyanogen bands.1 Fig. 10 gives the positions of the null lines and... 

Figure 11.6 Scan area by densitometry of HMW-GS by SDS-PAGE versus number of subunits for fhe sef of HMW-GS null lines. (From dafa of Lawrence, G. J. ef al. 1988. Journal of Cereal Science 7 109-112.)...

Figure 11.8 Extensigraph maximum resistance (Rmax) versus percentage glutenin in the protein for the HMW-GS null lines (open squares) and wheat/rye translocation lines (full squares). (Reproduced with permission from Gupta, R. B. et al. 1991. In Gluten proteins 1990, ed. W. Bushuk and R. Tkachuk, 71-80. St. Paul, MN American Association of Cereal Chemists.)...

If we assume that the equilibrium configuration of the nuclei represents an a-symmetric top, then the number of terms remains unaltered, just like the symmetry character. We therefore obtain ag lin two types of bands one type is symmetric in the neighbourhood of the null line (and the changes in the rotational spectrum are the same as in the pure rotation spectrum), and the others are only symmetric, when the two term systems appear with equal statistical weight (the changes of the rotational spectrum are different from the rotational spectrum). In the HaO spectrum one sees two basic vibrations (A — 6/x and A = 2.6/i). In the first the rotational spectrum can be observed and it is constructed symmetrically in the second it cannot be observed and it is not constructed symmetrically, A decision as to whether both easily combining term systems appear or only one, is for the time being not easily reached with the complicated construction of the H2O spectrum. When a precise analysis is possible in the future, it will use the relations presented in this section. 

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