Tutorial for Stopped-Flow Water Flux Measurements: Why a Report about “Ultrafast Water Permeation through Nanochannels with a Densely Fluorous Interior Surface” Is Flawed
Millions of years of evolution have produced proteinaceous water channels (aquaporins) that combine perfect selectivity with a transport rate at the edge of the diffusion limit. However, Itoh et al. recently claimed in <i>Science</i> that artificial channels are 100 times faster and almo...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2023-02-01
|
| Series: | Biomolecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2218-273X/13/3/431 |
| _version_ | 1827751053119979520 |
|---|---|
| author | Juergen Pfeffermann Peter Pohl |
| author_facet | Juergen Pfeffermann Peter Pohl |
| author_sort | Juergen Pfeffermann |
| collection | DOAJ |
| description | Millions of years of evolution have produced proteinaceous water channels (aquaporins) that combine perfect selectivity with a transport rate at the edge of the diffusion limit. However, Itoh et al. recently claimed in <i>Science</i> that artificial channels are 100 times faster and almost as selective. The published deflation kinetics of vesicles containing channels or channel elements indicate otherwise, since they do not demonstrate the facilitation of water transport. In an illustrated tutorial on the experimental basis of stopped-flow measurements, we point out flaws in data processing. In contrast to the assumption voiced in <i>Science</i>, individual vesicles cannot simultaneously shrink with two different kinetics. Moreover, vesicle deflation within the dead time of the instrument cannot be detected. Since flawed reports of ultrafast water channels in <i>Science</i> are not a one-hit-wonder as evidenced by a 2018 commentary by Horner and Pohl in <i>Science</i>, we further discuss the achievable limits of single-channel water permeability. After analyzing (i) diffusion limits for permeation through narrow channels and (ii) hydrodynamics in the surrounding reservoirs, we conclude that it is unlikely to fundamentally exceed the evolutionarily optimized water-channeling performance of the fastest aquaporins while maintaining near-perfect selectivity. |
| first_indexed | 2024-03-11T06:52:55Z |
| format | Article |
| id | doaj.art-c4b403c90de1434983b8e24e76c9bd10 |
| institution | Directory Open Access Journal |
| issn | 2218-273X |
| language | English |
| last_indexed | 2024-03-11T06:52:55Z |
| publishDate | 2023-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Biomolecules |
| spelling | doaj.art-c4b403c90de1434983b8e24e76c9bd102023-11-17T09:51:11ZengMDPI AGBiomolecules2218-273X2023-02-0113343110.3390/biom13030431Tutorial for Stopped-Flow Water Flux Measurements: Why a Report about “Ultrafast Water Permeation through Nanochannels with a Densely Fluorous Interior Surface” Is FlawedJuergen Pfeffermann0Peter Pohl1Institute of Biophysics, Johannes Kepler University, Gruberstraße 40, 4020 Linz, AustriaInstitute of Biophysics, Johannes Kepler University, Gruberstraße 40, 4020 Linz, AustriaMillions of years of evolution have produced proteinaceous water channels (aquaporins) that combine perfect selectivity with a transport rate at the edge of the diffusion limit. However, Itoh et al. recently claimed in <i>Science</i> that artificial channels are 100 times faster and almost as selective. The published deflation kinetics of vesicles containing channels or channel elements indicate otherwise, since they do not demonstrate the facilitation of water transport. In an illustrated tutorial on the experimental basis of stopped-flow measurements, we point out flaws in data processing. In contrast to the assumption voiced in <i>Science</i>, individual vesicles cannot simultaneously shrink with two different kinetics. Moreover, vesicle deflation within the dead time of the instrument cannot be detected. Since flawed reports of ultrafast water channels in <i>Science</i> are not a one-hit-wonder as evidenced by a 2018 commentary by Horner and Pohl in <i>Science</i>, we further discuss the achievable limits of single-channel water permeability. After analyzing (i) diffusion limits for permeation through narrow channels and (ii) hydrodynamics in the surrounding reservoirs, we conclude that it is unlikely to fundamentally exceed the evolutionarily optimized water-channeling performance of the fastest aquaporins while maintaining near-perfect selectivity.https://www.mdpi.com/2218-273X/13/3/431water channelaquaporinshydrodynamicsmembraneslight scatteringlipid vesicles |
| spellingShingle | Juergen Pfeffermann Peter Pohl Tutorial for Stopped-Flow Water Flux Measurements: Why a Report about “Ultrafast Water Permeation through Nanochannels with a Densely Fluorous Interior Surface” Is Flawed Biomolecules water channel aquaporins hydrodynamics membranes light scattering lipid vesicles |
| title | Tutorial for Stopped-Flow Water Flux Measurements: Why a Report about “Ultrafast Water Permeation through Nanochannels with a Densely Fluorous Interior Surface” Is Flawed |
| title_full | Tutorial for Stopped-Flow Water Flux Measurements: Why a Report about “Ultrafast Water Permeation through Nanochannels with a Densely Fluorous Interior Surface” Is Flawed |
| title_fullStr | Tutorial for Stopped-Flow Water Flux Measurements: Why a Report about “Ultrafast Water Permeation through Nanochannels with a Densely Fluorous Interior Surface” Is Flawed |
| title_full_unstemmed | Tutorial for Stopped-Flow Water Flux Measurements: Why a Report about “Ultrafast Water Permeation through Nanochannels with a Densely Fluorous Interior Surface” Is Flawed |
| title_short | Tutorial for Stopped-Flow Water Flux Measurements: Why a Report about “Ultrafast Water Permeation through Nanochannels with a Densely Fluorous Interior Surface” Is Flawed |
| title_sort | tutorial for stopped flow water flux measurements why a report about ultrafast water permeation through nanochannels with a densely fluorous interior surface is flawed |
| topic | water channel aquaporins hydrodynamics membranes light scattering lipid vesicles |
| url | https://www.mdpi.com/2218-273X/13/3/431 |
| work_keys_str_mv | AT juergenpfeffermann tutorialforstoppedflowwaterfluxmeasurementswhyareportaboutultrafastwaterpermeationthroughnanochannelswithadenselyfluorousinteriorsurfaceisflawed AT peterpohl tutorialforstoppedflowwaterfluxmeasurementswhyareportaboutultrafastwaterpermeationthroughnanochannelswithadenselyfluorousinteriorsurfaceisflawed |