The subsurface exploration of other planetary bodies can be used to unravel their geological history and assess their habitability. On Mars in particular, present-day habitable conditions may be restricted to the subsurface. Using a deep subsurface mine, we carried out a program of extraterrestrial analog research – MINe Analog Research (MINAR). MINAR aims to carry out the scientific study of the deep subsurface and test instrumentation designed for planetary surface exploration by investigating deep subsurface geology, whilst establishing the potential this technology has to be transferred into the mining industry. An integrated multi-instrument suite was used to investigate samples of representative evaporite minerals from a subsurface Permian evaporite sequence, in particular to assess mineral and elemental variations which provide small-scale regions of enhanced habitability. The instruments used were the Panoramic Camera emulator, Close-Up Imager, Raman spectrometer, Small Planetary Linear Impulse Tool, Ultrasonic drill and handheld X-ray diffraction (XRD). We present science results from the analog research and show that these instruments can be used to investigate in situ the geological context and mineralogical variations of a deep subsurface environment, and thus habitability, from millimetre to metre scales. We also show that these instruments are complementary. For example, the identification of primary evaporite minerals such as NaCl and KCl, which are difficult to detect by portable Raman spectrometers, can be accomplished with XRD. By contrast, Raman is highly effective at locating and detecting mineral inclusions in primary evaporite minerals. MINAR demonstrates the effective use of a deep subsurface environment for planetary instrument development, understanding the habitability of extreme deep subsurface environments on Earth and other planetary bodies, and advancing the use of space technology in economic mining.

The peptide Val–Arg–Arg–Pro–Asn–Leu–His–Pro–Ser–Phe–Ile–Ala–Ile–Pro–Pro–Lys–Lys–Ile, which corresponds to residues 84–101 of human κ-casein, has been synthesized and its conformation preferences determined by 1H-nuclear magnetic resonance spectroscopy in dimethyl sulphoxide. The peptide adopted a largely extended chain conformation in solution and there was evidence for the presence of a β-turn involving residues Pro87–His90 of human κ-casein. The presence of a turn in this position would make the physiologically significant Arg85 residue of human κ-casein (which is equivalent to Arg97 in bovine κ-casein) unavailable for interaction with Asp249of bovine chymosin, and may partly explain why human κ-casein is hydrolysed more slowly than its bovine counterpart by bovine chymosin.

The peptide Pro130–Thr–Ser–Thr–Pro–Thr–Ile–Glu–Ala–Val–Glu140–Ser–Thr–Val–Ala–Thr–Leu–Glu–Ala–Ser–Pro150–Glu–Val–Ile, which corresponds to residues 130–153 of κ-casein B, was synthesized and the conformation of the peptide in solution investigated by circular dichroism (CD) spectroscopy, structure prediction algorithms and 1H-nuclear magnetic resonance spectroscopy. In a solution containing the structure-enhancing solvent trifluoroethanol the CD spectrum was typical of a peptide in the α-helical conformation and nuclear magnetic resonance showed that the amino acids between Ile136 and Ser149 (κ-casein numbering) were predominantly in the α-helical conformation, but that Pro130 to Thr135 and Pro150 to Ile153 were not. In addition, Thr133–Pro134 and Ser149–Pro150 were primarily in the trans conformation, the residues from Thr131 to Thr135 were in unordered structures and the residues from Glu151 to Ile153 were in an extended conformation. Residues Glu137 to Glu140 and Thr145 to Ala148 also displayed some 310-helix character. When the peptide was dissolved in 10 mM-cetyltrimethylammonium chloride solution at pH 6, the CD spectra indicated that the proportion of helical structure was comparable to that of the peptide in trifluoroethanol solution (400 ml/l), whereas when the peptide was dissolved in buffer alone or in 10 mM-SDS solution, the CD spectra were consistent with a low helical content. Acidification of these solutions to pH 2·85 resulted in a slight increase in the helical content of the peptide in buffer and more markedly in buffer containing SDS. When the peptide was in 5 mM-CaCl2 solution at neutral pH, the CD spectrum indicated that some ordered structure was present. Taken together these results indicate that the ionizable residues Glu137, Glu140, Glu147 and Glu151 could be important in determining the stability of the putative helix. The structure predictions found that the sequence from Glu137 to Pro150 would be more likely to be in a helical than any other conformation in the intact bovine protein, but that pig, sheep and goat κ-caseins did not give a prediction of a strongly helical region in this part of the molecule.