# KALP15 in DPPC: Area per lipid is negative

**URL:** <https://gromacs.bioexcel.eu/t/kalp15-in-dppc-area-per-lipid-is-negative/435>\
**Category:** User discussions\
**Created:** [July 6, 2020, 5:23pm UTC](https://gromacs.bioexcel.eu/t/kalp15-in-dppc-area-per-lipid-is-negative/435 "2020-07-06T17:23:41Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![mikka](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@mikka](https://gromacs.bioexcel.eu/u/mikka)\
**Post date:** [July 6, 2020, 5:23pm UTC](https://gromacs.bioexcel.eu/t/kalp15-in-dppc-area-per-lipid-is-negative/435/1 "2020-07-06T17:23:42Z")

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GROMACS version: 2019  
GROMACS modification: No

I use the Justin Lemculus tutorial and enter the perl inflategro.pl system\_inflated\_em.gro 0.95 DPPC 0 system\_shrink1.gro 5 area\_shrink1.dat command, and it gives me:  
Area per protein, upper half: 1.75 nm ^ 2  
Area on lipid, top leaflet: -0.0277777777777777777778 nm ^ 2

Area per protein, lower half: 2 nm ^ 2  
Area on lipid, lower leaflet: -0.0317460317460317 nm ^ 2  
but before that it was  
Area per protein, upper half: 1.75 nm ^ 2  
Area on lipid, upper leaflet: 10.4755772444444 nm ^ 2

Area per protein, lower half: 2 nm ^ 2  
Area on lipid, lower leaflet: 10.4716089904762 nm ^ 2  
Why is the area negative? What could be the mistake ??