To search for further spectroscopic evidence for the aforementioned two types of hydrogen bonding interactions involving the phosphate group (i.e., *** HO-PrO- *** HO-[P.sub.i]+1-[O.sup.-]*** and [N.sub.2]-[H.sup.B]***O=P), we performed 2D [sup.1]H [right arrow] [sup.31]P HETCOR experiments.
Caption: FIGURE 7: (a) 2D 'H [right arrow] [sup.31]P HETCOR NMR spectra of the acidic 5'-GMP gel sample obtained at two different contact times (CT).
The resonance of the protonated carbons can be confirmed from the HETCOR
Solid state two-dimensional heteronuclear [C.sup.13]-[H.sup.1] correlation (HETCOR) NMR methods have been used successfully to assign spectra of macromolecules (Bielecki et al.
The crosspeaks in the HETCOR spectrum will primarily arise from interactions between [blank.sup.15]N atoms and directly attached protons.
The 2D HETCOR NMR spectrum of the mixture from the reaction of PMDI in water (cured at 1 10[degrees]C for 1 min.) is shown in Figure 2.
The 2D HETCOR NMR spectrum of the mixture from the reaction of PMDI in lignin (cured at 200[degrees]C for 1 min.) is shown in Figure 3.
The 2D HETCOR NMR spectrum of the mixture from the reaction of PMDI in cellulose (cured at 200[degrees]C for 1 min.) is shown in Figure 4.
Costing well below $100,000, the instrument can generate NMR spectra of 13C, 1H and 19F containing samples and perform 2D methods such as HMQC, HETCOR
, COSY and 2D JRES.
The 60 MHz instruments can perform most NMR experiments, including 1D 1H and 130, 2D COSY, HETCOR
and DEPT, for determining the structure of small organic molecules.
1), which was previously characterized by spectroscopy analysis as MS, IR and NMR including 2D sequences such as COSY, HETCOR
and COLOC (Pessoa et al.
NMR 2-D techniques such as COSY and HETCOR
are ever increasing in importance and use in chemistry.