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Incoming links: Quartz
The cell-free extract experiment under yeast asks whether fermentation requires intact living biological cells. In his 1907 lecture, Eduard Buchner described grinding yeast with quartz sand and diatomite in a large mortar using a heavy pestle, wrapping the dough in canvas, then squeezing it in a hydraulic press. Adding concentrated sugar syrup to the expressed liquid produced carbon dioxide bubbles and foam; separate investigations identified ethanol.[ref]
Cell-free fermentation by Eduard Buchner. Cell-free fermentation, Nobel lecture delivered 11 December 1907, printed pp. 110–112, Figures 2–4 and accompanying preparation/readout text
Activity persisted after filtration through cell-removing porcelain candles. Toluene inhibited live yeast fermentation while the cell-free extract retained activity, addressing a different objection from cell removal. These comparisons support extracted chemical machinery as the cause; bubbles alone would not identify alcoholic fermentation.[ref]
Cell-free fermentation by Eduard Buchner. Printed pp. 112–114: residual-cell objection, biscuit-porcelain filtration, toluene comparison and extract activity
The inference is activity outside intact living biological cells, not that biological cells are unnecessary for making or maintaining the machinery. Nor was this a purified single-enzyme mechanism: the lecture acknowledges unsuccessful purification and reports that two separated inactive fractions recovered fermentation when reunited. Such a reconstitution asks which components must work together, extending the initial separation of organism from chemical activity.[ref]
Cell-free fermentation by Eduard Buchner. Printed p. 115: unsuccessful zymase separation; pp. 117–118: gelatine-filter fractions and restored activity on reunion
A 2018 photonic experiment makes the distinction between populations and quantum coherence controllable. A 400-nm laser pumped a crystal to generate paired photons, filtered near 800 nm. One photon triggered collection; the other entered the apparatus. A half-wave plate and polarizing beam splitter selected horizontal photon polarization; another half-wave plate prepared balanced quantum superpositions. Separated polarization paths and diffraction gratings let a spatial light modulator control their frequency-dependent quantum phases and spectral weights. Recombined paths passed through quartz plates whose adjustable thickness controlled polarization–frequency coupling. Quarter- and half-wave plates plus a polarizing beam splitter selected tomography bases; jointly registered photodetector events supplied the readout. Quantum state tomography inferred polarization density matrices at each thickness. The dephasing model preserves diagonal populations while changing off-diagonal quantum coherence. Here the unobserved photon frequency acts as the environment for the polarization qubit. Finite modulator resolution and imperfect spectral shaping limited agreement with the intended dynamics; this experiment does not establish exact preparation or the ideal probabilities above. [ref]
Experimental implementation of fully controlled dephasing dynamics and synthetic spectral densities by Zhao-Di Liu and others. Experimental implementation of fully controlled dephasing dynamics and synthetic spectral densities, Nature Communications 9, 3453 (2018), Results: Experimental setup, Fig. 1, equations (1)–(5); Using a photon to simulate qubit coupled to Ising chain, systematic-error discussion after Fig. 3
In 1989, William E. Moerner and Lothar Kador reported individual pentacene absorbers in para-terphenyl in Optical detection and spectroscopy of single molecules in a solid by W. E. Moerner and L. Kador (pp. 2535–2538). Different local environments spread photon absorption frequencies; tuning into the sparse wings selected few resonant molecules despite many molecules in the illuminated volume.
Their tunable dye laser focused through a numerical aperture lens onto a – crystal immersed in superfluid helium at . Frequency modulation accompanied either a electric field between coated sapphire disks, detected at , or a quartz shear transducer. An avalanche photodiode measured transmitted-light photon absorption, not fluorescence. Double modulation suppressed residual laser amplitude background.[ref]
Optical detection and spectroscopy of single molecules in a solid by W. E. Moerner and L. Kador. pp. 2535–2537: sample, lens, dye laser, FM/Stark and FM/ultrasound apparatus and detection
Repeated scans gave the predicted modulated line shape. Blank crystals and off-resonance scans gave background; changing modulation frequency expanded and contracted the feature as predicted. Agreement between both perturbation methods supported the individual-absorber inference. The authors acknowledged out-of-focus molecules and the unlikely alternative of multiple absorbers with exactly coincident frequencies.[ref]
Optical detection and spectroscopy of single molecules in a solid by W. E. Moerner and L. Kador. Fig. 1(d–g), Fig. 2(b–g), and pp. 2537–2538: blanks, modulation-frequency changes, background and coincident-absorber qualification
This is evidence for a selected absorber in a prepared, known chemical substance and host. It does not establish arbitrary unknown molecule identity from one spectral feature, provide an atom-resolved photograph, or count every molecule in the crystal. A measurement sensitive to only a narrow excitation range cannot detect a molecule whose transition lies outside that range. This distinction separates the total particle inventory from the number responding to a particular probe.