You should not directly compare statistics calculated at different resolution, clearly the weak noisy reflectins will make the statistics worse even if the structure is better. The "paired refinement" procedure (Fig 1 of Science.336:1030-3. http://www.sciencemag.org/content/336/6084/1030.long) was designed to allow valid comparison and selection of useful resolution.

CC(1/2):   (-0.015) in the last shell at 1.8 suggests that may be pushing it a bit far.

It would be nice to compare the omit map made at 1.8 and 2.6 A.
eab

On 11/28/2015 06:21 AM, Greenstone talis wrote:

Dear All,

I initially got a 3.0 A dataset that I used for MR and refinement. Some months later I got better diffracting crystals and refined the structure with a new dataset at 2.6 A (for this, I preserved the original Rfree set).

Even though I knew I was in a reasonable resolution limit already, I was curious and I processed the data to 1.8 A and used it for refinement (again, I preserved the original Rfree set). I was surprised to see that despite the worst numbers, the maps look better (pictures and some numbers attached).

2.6 A dataset:

Rmeas: 0.167 (0.736)

I/sigma: 9.2 (2.2)

CC(1/2): 0.991 (0.718)

Completeness (%): 99.6 (99.7)

1.8 A dataset:

Resolution: 1.8 A

Rmeas: 0.247 (2.707)

I/sigma: 5.6 (0.3)

CC(1/2): 0.987  (-0.015)

Completeness (%): 66.7 (9.5)

I was expecting worst maps with the 1.8 A dataset...any explanations would be very appreciated.

Thank you,

Talis