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136    Cha pte r  F i v e


                       1.2

                   0.2  1.0
                                        50 μm        1073  1054 1026
                       0.8                               1006  42°C
     (a)          0.15                  Tip       1150  1104
                       0.6
                 TR
                   0.1
                       0.4                           1071  1048  1024
                                        50 μm     1151  1103  994
                  0.05                                      28°C
                       0.2
                                        Tip
     (b)       (c)  0.0  0.0
                        1800    1600   1400    1200   1000    800
                                                 –1
                                      Wavenumber (cm )
   FIGURE 5.4  (a) Photomicrographs of Aspergillus nidulans temperature-sensitive
   hypA1 morphogenesis mutant cells grown at (a) restrictive (42°C) and (b) permissive
   (28°C) temperatures. Bar (a) 50 μm, for both. (c) Synchrotron FTIR spectra of hypA1
   hyphae at tip and at 50 μm behind tip for growth at 28°C (red) and 42°C (black).
   Note the red and black log (1/R) scales for these temperatures. (Spectra
   reproduced from Ref. 9, with permission of Springer Verlag.)

                               1.4
                               1.3
                               1.2
                               1.1
                               1.0
                               0.9
                             TR  0.8
                               0.7
                               0.6
                               0.5
                               0.4
                               0.3
                               0.2
                                     3500  3000  2500  2000  1500  1000
                                                      –1
         (a)                  (b)           Wavenumbers (cm )
        FIGURE 5.5  (a) Photomicrograph of Neurospora hyphae grown on a gold-
        coated Si wafer. Refl ected light reveals rounded hyphal walls. (b) sFTIR
        spectra illustrating scattering artifacts arising from these rounded structures.

            Contamination of spectra from materials in the growth medium
        can be avoided by careful selection of analysis sites. Visual inspection
        of the prepared samples sometimes reveals a faint halo around the
        hyphae that are close to the agar block (Fig. 5.4c). Spectra from regions
        containing medium are compounded of both the mature hypha profile
        and the protein and sugar content of nonutilized medium. However,
        where the hyphae have successfully grown far out away from the
        medium, no such contamination appears; see also the nano-SIMS
        analyses described later in this chapter.
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