The structure of phycocyanobilin, the prosthetic group of phycocyanin, has been investigated by means of mass spectral, infrared, and nuclear magnetic resonance studies. The linear tetrapyrrolic compound has a molecular weight of 588 and contains an intramolecular hydrogen bond, the rupture of which forms the basis for several of the chemical transformations. Esterification, for example, is accompanied by dehydrogenation, so the molecular weight of the dimethyl ester is 614.The structure of the phycobilin P 655 has been deduced from an analysis of the properties of phycocyanobilin; this structure is nearly identical to the one proposed by Cole, Chapman, and Siegelman. For the phycobilin P 608 only a tentative structure can be presented.Phycocyanobilin is the prosthetic group of C-phycocyanin and allophycocyanin, both of which belong to the important class of photosynthetically active proteins of blue-green algae. Structural analysis of this coloured compound was started as long ago as 1933 when Lemberg and Bader [l] incorrectly identified it as the linear tetrapyrrole mesobiliviolin IXa. It was not until the extensive work of 6 hEocha [2] in 1963 that the complicated nature of phycocyanobilin became clear. 6 hEocha showed that three different pigments can be obtained, depending on the methods used to cleave the chromophore from the protein: he designated the three pigments he isolated P655, P630, and P608 on the basis of their Amax (nm) in acid chloroform. From the spectra of the pigment in the visible and ultraviolet regions, 6 hEocha concluded that the structure of the "native form" (P 630) was intermediate between that of mesobiliviolin and that of mesobiliverdin, but he was unable to give a detailed structure for phycocyanobilin at that time.We became interested in phycocyanobilin because of its assumed resemblance to the chromophore of phytochrome [3]. Since it is available in larger quantities than phytochrome we thought it an attractive model compound for our work on phytochrome: moreover with such powerful instrumental techniques as mass spectrometry, infrared spectrometry, and nuclear magnetic resonance spectrometry, we should be able to carry out a more detailed structural analysis than hitherto possible. During the course of our work two American research groups, namely Crespi and Katz [4,5] a t the Argonne National Laboratory, and Cole, Chapman, and Siegelman [6,7] a t the Brookhaven National Laboratory, reported the results of 39'their work on the structure of phycocyanobilin. Although the results of these two groups are in agreement as far as the nuclear magnetic resonance spectra are concerned, there remains a discrepancy between the mass spectrometry results: the former group found a molecular weight of 588 for the acid and the latter a molecular weight of 586, since they found the dimethyl ester to have a molecular weight of (We make extensive use of this notation in this paper, but the lettering has been omitted from the remaining Schemes for the sake of clarity.) Of great importance is the f...

Leakage of semi-rigid and flexible containers can be caused by faulty sealing or pinholes. Semi-rigid containers can be closed satisfactorily by removing product from the seal area during sealing. Biotesting indicates that pouches can be even more leakage-resistant than cans, provided the seal area is kept clean by proper filling. Careful handling keeps pinholes in these packs to an acceptably low level. Pouches experimentally punctured after processing result in low contamination provided they are immediately dried after cooling in chlorinated water. Large-scale production over several years of flexible pouches in Japan and semi-rigid containers in Europe has resulted in very little post-processing contamination.

15Pscanner unit, have been performed with 620, 350 and 280nm light. At all wavelengths sedimentationvelocity measurements gave identical results. Because of the magnitude of the extinction coefficient of the 620nm absorption band of phycocyanin, measurements could be made at concentrations as low as 0.005mg/ml. The monomer is not the only species present above concentrations of 0.01mg/ml. It is possible to stimulate disaggregation to monomer only by employing a pH of 3.9. Band sedimentation and conventional sedimentation-velocity measurements indicate that hexamer is the first aggregate formed. The aggregation process is analogous to a micellar process. The behaviour is consistent with a structural role for phycocyanin in addition to its known function as an energy-transfer pigment. Fluorescence measurements also indicate that the largest aggregates have the highest fluorescence efficiency (Lee & Berns, 1968a). The aggregation process in phycocyanin may be a prototype for membrane-forming systems.

The effect of handling flexible retort pouches has been studied in relation to their integrity and resistance to post‐process contamination (‘leaker spoilage’). Tests were made using a pilot‐plant processing line on which pouches were filled with broth, sealed, heat‐processed and subjected to three post‐process handling treatments. Using Enterobacter aerogenes as an indicator organism, it was shown initially that rough instead of careful handling during loading of the retort increased the proportion of punctured pouches from 0.06 to 0.27%. The effect of post‐process handling procedures on leaker spoilage was studied using pouches deliberately punctured with a needle of 100 μm diameter. When these pouches were cooled in tap water, unloaded manually from the retort and stored wet, the incidence of post‐process contamination was 90%. With similar pouches which were dried immediately after manual unloading and stored dry, the contamination rate was only 10%, whereas cooling in chlorinated water and drying before manual unloading reduced the contamination rate of punctured pouches to less than 1%. It was concluded that manual handling of dry pouches presents an acceptable alternative to complete mechanical handling of freshly heat‐processed pouches, which was proposed in a Code of Practice for retort pouches formulated in 1971.