Blackbody Infrared Radiative Dissociation BIRD

The blackbody infrared radiative dissociation (BIRD) technique can be considered as the reverse process of radiative association. At very low pressure, trapped ions (essentially in an ICR cell) are slowly dissociated by the blackbody radiation emitted by the walls of the ICR cell [127]. 

Many different gas-phase ion dissociations have been studied, including cation adducts with biomolecules. The models, on which the thermochemical interpretation of the data relies, depend on the size of the systems. In particular, it is easier to extract data from BIRD of large ion clusters, and most studies report data on the detachment of a small ligand from a large ion or cluster. The precision is similar to, or better than, that of RAK. 

---

In blackbody infrared radiative dissociation (BIRD) ions are activated by absorbtion of IR photons emitted from the walls of a heated ICR cell [19], The ICR cell is so far the only mass analyzer that meets both essential requirements for successful... 

Of course, thermochemistry in the form of bond energies can be measured by a variety of other experimental techniques. Key among these are temperature-de-pendent equilibrium methods [64-74]. More recently, absolute BDEs have also been measured using blackbody infrared radiative dissociation (BIRD) [75-81] and radiative association [82-84] methods. In addition, precise relative BDEs can be determined using equilibrium [85, 86] and kinetic method procedures [87-90]. Direct comparisons between results of TCID methods and those of these alternative techniques provide some confidence that all these various methods, when adequately interpreted, do yield accurate thermochemistry. 

The problem that the pre-exponential factor cannot be determined from quantitative IRMPD experiments can be circumvented by using an experiment which is called blackbody infrared radiative dissociation (BIRD). As in IRMPD experiments, BIRD is usually conducted in FTICR instruments. It does, however, require some special equipment, which is not always available. The BIRD experiment again is based on IR photon exchange with the ions in order to restore thermal equilib-... 

Fragmentation of peptide and protein ions in FT-ICR mass spectrometry may be induced by sustained off-resonance irradiation collision-induced dissociation (SORI-CID) [28], infrared multiphoton dissociation (IRMPD) [29,30], blackbody infrared radiative dissociation (BIRD) [31,32], surface-induced dissociation (SID) [33,34], and electron capture dissociation (ECD) [35,36]. These techniques are true MS/MS techniques in which the precursor ion is isolated prior to fragmentation. Additional techniques in which ions are not isolated but fragmented before they... 

Principles of Blackbody Infrared Radiative Dissociation (BIRD)... 

Gas-phase metal-ligand bond energies can be measured by a variety of experimental techniques. Measurements of absolute values can be made by temperature-dependent equilibrium methods, " " blackbody infrared radiative dissociation (BIRD), " radiative association, " and the TCID method discussed in detail here. Measurements of relative thermochemistry can be accomplished using equilibrium methods, the kinetic method, " and competitive CID (see Section 2.12.5.7). This review cannot include the details of all such measurements. 

Even under essentially perfect vacuum where collisional activation is virtually absent (< 10 mbar) ions can undergo slow unimolecular dissociation. As the energy for these fragmentations is provided by the emission of infrared photons by black-body radiation of the vacuum housing, this process is termed blackbody infrared radiative dissociation (BIRD) [157]. Blackbody infrared radiation is always present above non-zero temperatures. BIRD dissociations are characterized by reaction times in the order of several seconds to even minutes. Therefore, ICR cells provide the most suitable environment for their study. To vary the wavelength and intensity of IR radiation both the ICR cell and the surrounding vacuum manifold have to be uniformly heated. Typically, temperatures up to about 250°C can be reached in dedicated instruments. This allows to study reaction kinetics where bonds of low to moderate strength are involved [157]. 

Examples from other groups include gas-phase thermal dissociation experiments, implemented with blackbody infrared radiative dissociation (BIRD) and FT-ICR MS on a series of protein-carbohydrate complexes, and the detection of fusion peptide-phospholipid noncovalent interactions using nano-ESI FTICR-MS. An interesting example of protein-DNA interaction smdied by ESI-MS is the trp repressor-DNA operator complex. Escherichia coli trp apo-repressor (TrpR), a homodimer, is a DNA-binding protein that binds to two molecules of co-repressor L-tryptophan to form a holorepressor complex at higher salt concentrations. The mass spectrum of noncovalent... 

---