The following table describes the format of the oligonucleotide modification information listed in the "Mod" column in the Results tables on the Process and Review page.

Modification notation information

Modification type

Description

FLP

Full-length product; no modification.

Variable modification

For example, 3:A9–T15 = 2104.4033M(A9+Deamination) shows:

  • A9 = the modification occurs at the adenine at position 9 in oligonucleotide 3
  • Deamination = the modification type

Multiple modifications

For example, 7G1–C15 = 4671.7648m[3’p](C6+C Depyrimidination) shows two modifications:

  • A phosphate group (p) at the 3’ terminal (C15 end) of the sequence 7G1–C15 in oligonucleotide 7
  • A depyrimidination at base C6 in the sequence 7G1–C15 in oligonucleotide 7

Unspecified modification

An unspecified modification is the addition or subtraction of a given mass of unspecified origin.

For example, 6:A1–G17 = 5159.9221m(~C10+14.0137) shows:

  • ~C10 = the modification is on the C base at position 10 (approximately) in oligonucleotide 6
  • +14.0137= the addition of a mass of 14.0137 amu

The Enable Mass Search for Unspecified Modifications option must be selected in the processing method (Parameters > Identification > Advanced Search) for the application to perform these identifications.

[(5')n-x] or [(3')n-x]

(Nonspecific cleavage)

For example, 3:C3–T15 = 3917.6985m[(5')n-2] shows that the identified component (bases C3-T15 on oligonucleotide 3) is the result of two base losses from the 5'-terminal of the oligonucleotide full-length product (FLP).

Similarly, 1:G1-A15=42595.034a[(3')n-2) shows that the identified component (bases G1-A15 on oligonucleotide 1) is the result of two base losses from the 3'-terminal of the FLP.

Note: Nonspecific cleavages are reported only for oligonucleotides with no ribonuclease specified.

3’-terminal modifications

The 3’-terminal of an oligonucleotide can be modified with the following groups:

  • Phosphate (p): H3PO4
  • Phosphorothioate (s): H3PO3S
  • 3’-Triantennery GalNAc (g): C78H140N11O34P

For example, 7:G10–C21 = 3726.378m[3’p] shows that the 3’-terminal (C21 end) of the sequence G10–C21 of oligonucleotide 7 has been modified with a phosphate (p) group.

5’-terminal modifications

The 5’-terminal of an oligonucleotide can be modified with the following groups:

  • Phosphate (p): H3PO4
  • Phosphorothioate (s): H3PO3S
  • Biotin (b): C10H16N2O3S
  • cAG (a): C32H44O27N15P5
  • cAU (u): C31H43O28N12P5
  • cARCA (r): C22H32O21N10P4
  • mCAP (c): C21H30O21N10P4

For example, 1:A26-G28 = 997.15180m[5'p] shows that the 5’-terminal (A26 end) of the sequence A26–G28 of oligonucleotide 1 has been modified with a phosphate (p) group.

Adducts

For example, 8:T1–G24 = 7342.2761m(Na+) shows that the oligonucleotide is a Na+ adduct.

The application detects adducts when an identified mass is higher than the expected precursor mass by a specific amount, for example, ~22 amu higher for a Na+ adduct, based on the given charge state.

The application search for many possible adducts, including Na+, 2Na+, Ca+2, and Fe+3.

Deletion

A deletion (residual loss) is the loss of a nucleotide base within a given sequence identification.

The Enable Residue Deletion option must be selected in the processing method (Parameters > Identification > Advanced Search) for the application to perform these identifications.

The “Site” column in the Results table displays the deleted nucleotide base.

For example, 1:U1–G6 = 1897.3107m(G4+Deletion) shows that the application detected that nucleotide base G4 was deleted from the sequence U1–G6 in oligonucleotide 1. The Site column displays “G4”.

NOTE

A tilde (~) displayed before a base site (~G11) indicates that the position of the identified modification is approximate (less definite).