. 2019 Sep 23;63(10):e00564-19. doi: 10.1128/AAC.00564-19

TABLE 4.

Observed and calculated masses of KPC variants before and after modification due to DBO treatment

Carbapenemase by DBO treatment	Mass (Da) of:				Assignment^d
Carbapenemase by DBO treatment	Observed^a	Calculated^b	Shift(s) observed^c	Shift calculated	Assignment^d
KPC-2	30,640	30,640
+avibactam	30,905	30,905	+265	+265	acyl
	30,826	30,825	+186	+185	acyl-80
	30,808	30,807	+168	+167	acyl-98
+relebactam	30,989	30,988	+349	+348	acyl
	30,907	30,908	+267	+268	acyl-80
	30,890	30,890	+250	+250	acyl-98
KPC-3	30,665	30,667
+avibactam	30,931	30,932	+266	+265	acyl
	30,851	30,852	+186	+185	acyl-80
	30,834	30,834	+167	+167	acyl-98
+relebactam	31,013	31,015	+348	+348	acyl
	30,935	30,935	+270	+268	acyl-80
	30,914	30,917	+249	+250	acyl-98
KPC-4	30,657	30,657
+avibactam	30,922	30,922	+265	+265	acyl
	30,841	30,842	+184	+185	acyl-80
	30,824	30,824	+167	+167	acyl-98
+relebactam	31,005	31,005	+348	+348	acyl
	30,924	30,925	+267	+268	acyl-80
	30,908	30,907	+251	+250	acyl-98

Masses implied from maximum entropy deconvolution of measured spectra.

Masses were calculated based on protein sequences without an N-terminal methionine. All differences between measured and expected masses are within experimental error.

Corresponding to the observed protein masses.

Acyl denotes a mass shift corresponding to reaction of an intact DBO molecule. A chemical scheme depicting the assigned acyl, acyl-80, and acyl-98 species is displayed in Fig. 5A.